Asta and Liebe vs. Nacht Faust

Asta and Liebe vs. Nacht is a fight that occurs as part of Asta's training.

Pre-Fight
Nacht congratulates Asta on forming a contract with Liebe and believes Asta is in the right for making a contract based on friendship. Nacht wants Asta to get stronger since those who are right are not necessarily rewarded. Gimodelo then enters Nacht's shadow and emerges as his larger self. Nacht then unites with Gimodelo and tells Asta and Liebe that the next part of their training is to defeat him.

Fight
Nacht explains that Asta has to unite with Liebe, to draw out more Anti Magic, and attacks the two with Shadow Magic. Asta enters his black form and dispels the shadows that are binding the two. Asta notices that Liebe has shrunk and is on Asta's shoulder. Nacht explains how he can enter Union easily since he is the one controlling his contracts, and explains that what Asta's black form is not Union. Asta asks Liebe how to enter Union, but Liebe says that he does not know and was just going to take over Asta's body. Nacht explains that Asta will have to figure it out on his own.

Nacht then demonstrates how Unite Mode allows him to add his devils' characteristics to Shadow Magic. Gimodelo's characteristic is "Pack", and Nacht creates a horde of dog-like clones made of shadow. Nacht has the clones attack, and Asta struggles to block and dodge their attacks. Nacht tells Asta that the wolves will not disappear until he is defeated. As he cycles through his swords, Asta thinks about how his connection with Liebe is stronger, but Nacht points out that drawing out the power will not be easy for Asta since Liebe is not his servant. After grabbing Yami Sukehiro's katana, Asta says that he will surpass his limits, which irritates Nacht, disrupting his ki. Asta senses the disturbance and sends a flying Anti Magic slash, which cuts the edge of Nacht's cloak. Asta decides to name the katana, the Demon-Slasher Katana, and restates that he is going to surpass his limit. Nacht mentions that he hates that phrase.

After two days, Asta and Liebe continue to fail, and Asta notes that the injuries he receives in his black form are shared with Liebe now. The two eat cookies filled with Healing Magic from the Spade Kingdom's Resistance. Once their wounds are healed, Asta suggests a lame idea that Liebe goes along with on the chance of it being successful. When it too fails, Asta and Liebe begin bickering, but Nacht interrupts and informs them that their time is up. He then engulfs the two with his Dark Prison Hunting Ground spell. As Nacht attacks them, Asta enters his black form and notices that he cannot dodge the attacks since he cannot sense their ki. As Nacht continues his attacks, Asta and Liebe wonder why they cannot unite and think about why they want to get stronger. They both resolve not to let the other die. In that moment of shared desperation and determination, Asta and Liebe manage to unite, shining within the darkness of Nacht's spell. Asta manages to release a single slash that cuts through Nacht's spell and negated part of Nacht's transformation, even though the slash did not touch him. Impressed by Anti Magic's and Asta's potentials, Nacht admits defeat.

Post-Fight
Although Asta and Liebe achieved a union, Nacht refuses to let them join the mission yet since they need more time to master it. Nacht leaves Gimodelo behind to continue their training, and the devil shivers in fear of that Anti Magic attack.