Episode 136

A Black Deep-Sea Story (黒の深海物語) is the 136th Page of Yūki Tabata's Black Clover.

Summary
Deep beneath the ocean, the priests of the Seabed Temple attempt to calm a guardian of the sea who was going berserk. Gio, having dubbed their efforts to be not enough, ordered Kiato and Kahono to retreat so that they could try again later.

Up on land, the Black Bulls are training on the beach. Since the area has a strong presence of natural mana, it is an excellent place for mages to get stronger; water mages especially, being that it is by the ocean. While Noelle Silva is working on her control, she hears a strange song. She cannot identify it, but for some reason, it makes her feel nostalgic. Before she can think about it, she is interrupted by Asta, Magna Swing, Luck Voltia, and Finral Roulacase, who are participating in physical training. Finral falls behind and asks why they are not just practicing magic. Magna replied that Asta, as well as Captain Yami Sukehiro, had proved during the recent battle with the Elf Tribe that muscles are just as important as magic. Before they could continue their workout, Asta, Magna, and Finral fell into a pitfall, created by Zora Ideale, who had been practicing his Trap Magic.

After the team took a break for lunch, Noelle heard the song again. She ran to investigate and was followed by Asta. Suddenly, Kahono and Kiato, emerge from the ocean and ask for their help.

When the Black Bulls arrive at the Seabed Temple, High Priest Gifso explains that the temple guardians were injured trying calm a monster, a guardian of the sea who serves the Sea God, who had become restless due to an unexplained instability of the undersea mana. Gifso begs the Magic Knights to lend them their great strength. Noelle proposed that she could create a smaller, but more durable version of her Sea Dragon's Cradle, which would allow four people, herself, Kahono, Kiato, and one other mage to safely reach the aggressive guardian. Asta, Luck, Gauche Adlai, and Charmy Pappitson all desire to be the fourth, each with their own reasons. Yami ultimately decides that Finral will be the fourth team member, as he could use his Spatial Magic to get them out of danger.

The team descends down an undersea cavern known as the Void of No Return. On the way down, they are confronted by a strange group of fishman warriors, originally ordinary sea life that had been transformed into monsters by the unstable mana in the sea. Kahono and Kiato attempt to fight them off, but they manage to break through Noelle's protective bubble. She remembers what Lolopechka said about the Spirit Guardians being able to use natural mana. Noelle puts this into practice and creates a Sea Dragon's Cradle around herself and more of them around each of her teammates. After making it past the fish monsters, they were confronted by another guardian of the sea, the Kraken. The giant squid releases a shroud of ink, obscuring their vision and disrupting the surrounding mana. Noelle manages to strike the creature down using her Valkyrie Dress. They continue onward until finally reaching the bottom of the cavern.

The group find themselves in an ancient ruin of undisclosed origin, before they can discuss the ruin in detail, the guardian, a white whale with a blue lion's mane, ram-like horns, and jellyfish-like tentacles coming from the base of its head, emerges from the shadows. Kahono and Kiato begin the ritual to calm the beast. It appears to be working, but while the guardian was enjoying the performance, the mages discover the reason why the guardian had been so aggressive lately. The guardian was being protective of its baby. As the guardian and its baby were soothed by the ritual, the volatile mana in the ocean returned to its normal state, and the transformed sea creatures along with it. Noelle realizes that the song she was hearing earlier was the lullaby that the guardian was singing to its baby. Before leaving, the guardian touched its nose to Noelle's forehead, showing her an image of her mother.

After returning to the beach, Kahono questioned if the Magic Knights were really satisfied with the small amount of sea food that they had been given as a reward. Kahono proposes that the she, Kiato, Noelle, and Asta go on another double date some time, like they did during the Star Awards Festival. Asta immediately accepted, which Noelle scolded him for, telling him not to answer for her. Finral begins to swoon over Kahono from behind a rock, but immediately reminds himself about Finesse Calmreich. Yami joins him and notes how far the spatial mage has come, noting that his progress really began during their first visited Seabed Temple.

Trivia

 * This episode mistakenly has Noelle use Mana Method before her training in the Heart Kingdom.
 * For the home release versions, the rune arrays were changed to ripples of water.