|“||The ones you looked down on and stepped on and toyed with are going to defeat you today!!||”|
Secre Swallowtail 「セクレ・スワロテイル Sekure Suwaroteiru」 is the servant of Lemiel Silvamillion Clover, prince of the Clover Kingdom and the first Magic Emperor. She is transformed into an anti-bird named Nero after sealing Lemiel into a statue.
Five centuries later, she decides to stay alongside Asta after encountering him at the beginning of the Magic Knights Entrance Exam, and is later accepted herself as a member of the Black Bull squad of the Magic Knights.
As a human, Secre is a slender woman with black hair in a bob style. Two locks of hair stick up from the top of her head. She has dark bags under her eyes. She wears a black dress with thin straps and a short, ruffled skirt that resembles feathers. Due to using Forbidden Magic, she grows two black horns on the sides of her head.
As an anti-bird, Nero is a very small bird with a pair of sleek wings, a pair of tails that form an arrow at the tip and a black beak. Nero's feathers are black at the back, white at the front, and red on her face. In addition, Nero also possesses a pair of horns on either side her head and a pair of long black feathers sticking up from the top of her head.
One of her notable features is her slanted eyes that give Nero a hostile aura. The design of her eyes are present in both Nero's human and anti-bird form.
Furthermore, the feathers around Nero's neck have a fuzzier texture then the rest of her feathers, which creates the sense of wearing a collar around her neck.
Secre is generally apathetic. When she becomes annoyed, she repeatedly pecks at Asta's head or pulls on his hair. Additionally, she also has a penchant to use this tactic to get her thoughts across to others as well, or when she is disagreeing with them.
In contrast to the way she treats him, Secre is very loyal to Asta, as she rarely leaves his side. She also constantly helps Asta in every predicament, such as guiding him through the dungeon or showing him the path to an artifact behind the wall. She also possesses a strong sense of loyalty and devotion to Prince Lemiel Silvamillion Clover, having defied natural law to keep him alive and caused herself to be sealed as a bird, and despite this, she still retained her strong sense of loyalty towards him and she even went as far as stating that she would gladly follow him to the afterlife when his body began to crumble after exhausting his power.
Secre is assigned to serve Prince Lemiel Silvamillion Clover, and together they work to create various magic tools. One day she follows Lemiel and his sister, Tetia, when they sneak out of the castle to visit the Elf Tribe.
On Tetia and Licht's wedding day, Secre hears Lemiel calling for help and finds him bound by magic. She reports that the magic siphon was stolen and unseals the prince. They fly to the wedding venue but are too late. The magic tool was used to kill the elves and Tetia, and Licht's grimoire has become corrupted. To prevent the devil from taking his body, Licht uses the magic stones to transform himself into a giant demon. While Lemiel fights the monster, Secre gathers the magic siphon and the magic stones. Lemiel uses the siphon to absorb the monster's magic. Although the tool breaks, it weakens Licht enough for Lemiel to kill him.
Secre uses the magic stones to seal the devil, and the magic causes two horns to grow from her head. Before her spell finishes, the devil calls the stones over and uses them to cast Reincarnation Magic on the elves, planning to return with them. Since Lemiel is fatally injured during the fight, Secre uses the stones again and seals the prince in a statue atop the Demon God's skeleton on the outskirts of Hage. Due to the overuse of Forbidden Magic, she is transformed into an anti-bird.
Five centuries later, Secre and a flock of anti-birds are present when the Magic Knights Entrance Exam is held. They pester several examinees prior to the start of the exam. After she encounters Asta, Secre decides to land on top of his head and sneaks into his clothes for a couple of days without revealing herself to the former.
After Asta's fight with Heath Grice ends, Secre decides to come out of Asta's clothes and takes off to observe the Sosshi village from above. She then locates the magic stone within the attic of the village church. Secre takes it to Asta and uses it to peck Asta's head in order to wake him up. Secre then tries to hold the item as tight as possible when Asta tries to take it from her with the intention to return it to the villagers.
Afterwards, Secre begins to chase Asta around the village while pecking his head, with Noelle Silva following them from behind. She then lands on top of Asta's head while the latter is giving a few words of encouragement to one of the children of the village.
Secre then follows Asta, Magna Swing, and Noelle back to the Black Bull base to report about the mission. During that time, Secre meets Vanessa Enoteca, who compliments the cute little creature. Later on, Secre follows Asta, Noelle, and Vanessa's venture to Kikka, where she remains in close proximity to Asta.
When Yami Sukehiro informs several Black Bull members about the emergence of a new dungeon, Secre sits on top of Asta's head while Noelle pets her. Subsequently, she joins Asta, Luck Voltia, and Noelle to the dungeon when they are assigned a mission to conquer it. On their way to the inner-side of the dungeon, Asta and Noelle start arguing on the name that they should use to address Secre. The argument heats up when the bird begins to peck Asta's head to show disagreement of his suggestion. However, Secre quickly agrees to Luck's suggestion.
After they walk in the dark for quite sometime, they finally arrive at the inner-side of the dungeon. During the time, Secre remains silent when Luck pulls a prank on Asta and Noelle and leaves almost immediately and when a trap is activated and Yuno saves Asta and Noelle from it.
Secre continues to remain silent while Asta and Noelle have a conversation with the Golden Dawns Klaus Lunettes, Yuno, and Mimosa Vermillion. Later on, after both teams go their separate ways, Asta and Noelle continue to explore the dungeon. Secre finally breaks her silence by showing them a path after she sees that both Black Bulls do not know which direction they need to go. Asta and Noelle are still unable to reach their destination as they are lost in an area with an unusual gravitational field. When Asta tries to ask Secre about it, the bird decides to ignore him and returns to being silent while watching both of them.
After a while, Secre, Asta, and Noelle finally find the correct path and cruise through it towards the center of the dungeon until Asta decides to take a detour to save Luck. While the Black Bulls fight against Lotus Whomalt of the Diamond Kingdom, Secre lands on top of Asta's head, but quickly flies away to avoid being a hindrance to them. After Lotus is defeated and manages to escape, Secre follows the Black Bulls to the center of the dungeon. When she arrives along with Noelle and Luck, Secre sees that Asta and Yuno are prepared to fight against another Diamond Kingdom's mage, Mars.
After Asta manages to render Mars unconscious, Secre returns to Asta and lands on top of his head. Not long after they enter the dungeon's treasury, Secre quickly tugs Asta towards a wall that has the same locking mechanism as the door to the treasury. She then immediately starts pecking Asta on his head when the boy does not understand the hint.
Suddenly, Mars breaks through the treasury's door and manages to incapacitate everyone except Asta and Mimosa. Mars then sends Asta crashing through the wall that Secre showed to Asta earlier. Seeing that Asta is inside the hidden room, Secre quickly follows and flies over him before landing on the pommel of a sword covered with dirt. After Asta is finally able to understand Secre's hint, the boy takes the sword and resumes his fight.
After Mars is instantaneously defeated by Yuno, Secre remains close to the fainted Asta as all of them rush towards the exit as the dungeon is collapsing. The anti-bird immediately lands on top of Asta's head, the moment the boy awakes and Klaus suddenly hugs him.
A week after the mission, at the Black Bull's headquarters, Secre joins Asta on a feast that is given to the latter for his performance during the mission. She also remains close when Asta and Noelle need to go to the Magic Knights headquarters in the Noble Region to report about the mission. Secre remains silent and does not bother Asta in anyway while the latter is in audience with the 28th Magic Emperor, Julius Novachrono, nor when he is attending the ceremony and banquet that honors several members of the Magic Knights.
However, when Asta begins to get annoyed while his comrades are being humiliated by those honorary Knights, Secre decides to take off from Asta's head as she watches the latter confronting them. After the commotion dies down when someone enters the banquet hall to inform the Knights that the Royal Capital has been invaded, Secre returns to Asta's side as the latter joins the Knights' discussion regarding their counterattack strategy. Not long after, the anti-bird follows Asta when the latter decides to move out before the others. Secre remains by Asta's side until they find the man behind the invasion, Rades Spirito.
While Asta is fighting against Rades, Secre stays on top of a little girl's head that Asta saved from the terrorist. Secre remains unruffled even when the little girl is about to be attacked and Noelle steps in to protect her in Asta's place. Afterwards, Secre stays put on top of the little girl's head while they are observing the fight from afar. When Asta returns with the Magic Emperor after being captured by members of the Eye of the Midnight Sun, Secre immediately leaves the little girl's head and greets Asta by pecking his head.
Later on, Secre stays on top of Asta's head as the Black Bull members prepare their departure from the Royal Capital. The anti-bird also remains composed when Yuno sends his farewell to Asta by launching an attack towards him. As they arrive at the Black Bull's headquarters, Secre keeps herself comfortable on top of Asta's head while the Black Bull members are having a conversation around him.
During a blind date, which Asta attends alongside Luck and Finral Roulacase, Secre remains in silence as she observes from the top of Asta's head. However, when Secre notices Sekke Bronzazza is also on a blind date, the anti-bird quickly takes off to the latter's table and intensely observes him. Secre then shifts her attention and observes Asta, alongside Noelle, when the boy is taken into an alley by his date, Rebecca Scarlet. At the end, Secre returns to Asta's head as the latter asks Rebecca the purpose of a blind date.
Secre then stays by Asta's side when the latter visits Rebecca in Nairn. The anti-bird flies away when Gauche Adlai assaults Asta. After returning to Asta's head, Secre then discovers Noelle who is watching them from afar. She approaches the noblewoman and stares at her as Noelle learns about Asta's decision to stay at Rebecca's house. After dinner, Secre goes to sleep next to Asta in one of the bedrooms. However, the moment Gauche sneaks into the bedroom and causes some havoc, Secre quickly flies outside from the hole, which the mirror mage made. When they realize that the children of Nairn have gone missing, Asta and Gauche, along with Sister Theresa from the church, set forth to pursue them. However, Secre decides to stay at the town alongside Noelle and Rebecca.
Back in the house, Secre sits on Pem's head while Noelle reports to the Magic Knights. Secre settles on the window sill, staring out and waiting. Secre reunites with Asta after he returns from meeting with the Magic Emperor. She then sits on his head when he returns to Nairn. Marco returns Asta's squad robe and Rebecca kisses Asta's cheek.
Secre accompanies the Black Bulls on a party on Raque's beach. She settles in a nest next to Vanessa's chair. A week later, Secre secretly follows the Black Bulls into the Seabed Temple. She locates the magic stone and brings to the Black Bulls after Temple Battle Royale. She returns to sitting on Asta's head when they all leave the temple and return to the base.
She sits quietly as Asta travels to the Royal Capital to report to Julius. The meeting is interrupted by a report that the Diamond Kingdom is attacking Kiten. The Black Bulls travel to Kiten and Secre stays near Asta who tries to direct the citizens to safety. However, she stays behind when Asta launches himself at Yagos.
Secre accompanies Asta on his visit to Owen. She stays with him during the celebratory feast. Later, Asta goes off to contemplate his diagnosis and Secre sits next to him on the rock. The next morning, she is back to sitting on his head and shoulder while he wanders the base.
Secre follows Asta to the Witches' Forest. After all of the fighting is over, Secre lands on the Witch Queen's shoulder and pecks her magic stone earring. When the Black Bulls return to the queen's throne room, Secre sits on Asta's head while the queen hands over the stone and tells them about the Elf Tribe. She remains on Asta's head while the Black Bulls bid farewell to their new friends, return to their base, and greet the other returning Black Bulls.
A week later, Secre accompanies Charmy Pappitson to the Royal Knights Selection Exam. She hides the two of them in a ball of cotton within Noelle's hood. Secre silently watches the matches from atop Charmy's head.
Several days after the exam, Secre hides in Asta's clothes before the boy is taken away by Mereoleona. Secre pops out when Licht confronts Asta and Yuno. The bird pecks at Asta's forehead but flies away to avoid Licht's attacks. She sits on Mimosa's head and watches the fight. When Licht blasts the humans out of the dungeon, Yuno protects Secre and Mimosa as they all fall down into the water below. Secre remains on Mimosa's head while the remaining Royal Knights regroup on the lake shore and decide to return and defend the kingdom.
The bird follows Asta and Yuno when the two leave to defend Hage from attack. She watches the fight from the church's steeple and flies down after Asta exorcises the elf spirit. She then settles on Asta's head and travels with the boy to a town in the Common Region. She watches the fight from afar and, after Lufulu is exorcised, flies down to settle on Asta's head again. She remains on Asta's head while the Black Bulls return to their base and they travel to Hecairo. She remains in the base when Asta is fired from a cannon.
After Drowa is exorcised, Secre flies over and sits on Gauche's head. She stays on Gauche's head when the Black Bulls remain behind to fight a group of possessed Golden Dawns. Secre reacts to Yuno's magic stone opening a gate to the Shadow Palace. The bird follows Yuno and Charmy but the gate closes before she can enter.
Secre flies over to the destroyed throne room of Clover Castle where Finral has finished recovering. Secre pecks at the Black Bull's forehead and then asks to be taken to the Demon God's skeleton. After Finral teleports them there, Secre has him take the magic stones from the tablet and place them in the First Magic Emperor's statue. This breaks the seals on Secre and the statue. Secre returns to her human form and welcomes back her prince. She coldly stares back when Finral tries to hit on her. She then grabs Lemiel's and Finral's hands so the prince can launch them all back to the castle. Along the way, Secre reopens the gate into the Shadow Palace and drops Finral in the throne room. As they pass through the gate, Secre reflects on her past with Lemiel and the elves.
Secre and Lemiel appear in the topmost chamber, and she uses her magic to unseal Licht's soul. She watches as Lemiel and Licht team up to fight the devil and its magic, and panics when the devil severs Lemiel's arm. After Asta blocks the devil's trident, the devil summons another Storm of Swords, which Licht, Lemiel, Yuno, and Patolli knock down. Secre grabs one of the weapons, flies up to Lemiel, and reattaches his arm. Asta compliments her magic and notes that she seems familiar, but Secre tells him to focus on the battle. When the devil belittles their magic, Secre tells him to be quiet and that their magic will defeat him.
Secre watches as Licht draws on the other elves' magic to power a spell to destroy the devil. However, the devil survives and regenerates his body. Asta tries to imitate the Licht's spell, and when Lemiel asks about the boy's sword, Secre explains that another devil took up residence in Licht's grimoire and Asta uses its Anti Magic. When the devil summons more monstrous creatures to overwhelm the boy, Lemiel grabs Asta and tries to fly with him but Asta accidentally hits Lemiel into a wall. Secre flies over to the prince and offers to seal Asta's power which is becoming more uncontrolled, but Lemiel suggests that she wait. When Asta succeeds in controlling the Anti Magic, Secre explains to Lemiel that Asta is a magic-less idiot who refuses to give up. Asta and Yuno work together to stab the devil, who in response summons even more creatures from the underworld, threatening to swallow the Shadow Palace. Despite the overwhelming threat, Secre believes in Asta and tells him to win.
Secre flies over to Licht and Lemiel as they send out protective auras to the elves, and Patolli protects the three of them from the devil's magic. Asta and Yuno manage to pin the devil between their two swords, but Asta's black form gives out. Yami then uses Dark Cloaked Dimension Slash: Equinox to cut the devil in half, and Secre takes the opening to seal Asta's physical strain, allowing him to pull off one more Black Divider and to destroy the devil's heart. Secre then thanks Asta and Yuno for ending the centuries of strife.
Once the humans and elves are all gathered in the topmost chamber, they pass through the exit and return to Clover Castle. After the remaining elf spirits are exorcised by the combined effort of William, Licht, and Asta, Secre stands with Lemiel on a broken tower and look out over the kingdom, while Mimosa, Asta, and Noelle are nearby. When Asta asks if she is Nero, she confirms and explains that she was originally human and could not speak as a bird until the Shadow Palace was summoned. She then pulls on his cheek and reprimands him for acting like Lemiel. Suddenly Lemiel's body starts cracking apart. Secre wishes to go with him, but he tells her to live on. She clutches his hand as he crumbles away and thanks her for everything she has done over the five centuries.
- Sealing Magic: Secre uses this magic attribute to open and close objects and other spells. She is also capable of sealing people into objects and later develops the ability to seal herself into the form of an anti-bird at will.
- Mana Sensory: Secre possesses the ability to sense mana within living creatures and inanimate objects. Additionally, her abilities allows her to locate magic items from a long distance and through walls. She also could use it to determine the quickest path towards the mana that she is sensing.
- "The ones you looked down on and stepped on and toyed with are going to defeat you today!!" 「アナタが見下し踏みつけ弄んできたものにアナタは今日 敗れる...!! "Anata ga mikudashi fumitsuke moteasonde kita mono ni anata wa kyō yabureru...!!"」
- Asta wishes to name her "Toritarou" 「トリタロウ」 while Noelle wishes to name her "Sylvants Schnauzer" 「シルヴァンタス シュナウザー Shiruvantasu Shunauzā」 before agreeing on Luck's suggestion, Nero, which means "black" in Italian.
- Nero may also be a reference to the Roman emperor Nerō Claudius Caesar Augustus Germanicus.
- As Nero, Secre ranked #5 in the first popularity poll, #19 in the second, and #16 in the third.
- Secre's favorite things are soft and fluffy objects.
- As an anti-bird, her favorite things are the tops of people's heads (the softer, the better).
- Secre's grimoire design is the background for Volume 22's cover.