Nighteye Squad vs. Joi Irinaka is a battle fought between Sir Nighteye's group including Sir Nighteye, Eraser Head and Deku against Shie Hassaikai General Manager Mimic during the Shie Hassaikai Raid.
Following the skirmish between Himiko, Twice and the heroes, Mimic helps his "allies" fall back into a safe space within the underground cave. Twice starts freaking out after losing to Sir Nighteye but Himiko calms him. She understands that working with the Yakuza after Magne's death isn't easy.
However, Tomura Shigaraki lent them to the Yakuza so he can take responsibility for what happened. Twice and Himiko know Tomura has set them free for the sake of the League of Villains, and they're permitted to act as they want.
Himiko insults Mimic for being a useless ally. The duo tells Mimic that it's weaklings like him that have brought the Yakuza to the brink of extinction. Mimic loses his temper after Himiko insults the bedridden Yakuza boss.
Mimic shifts the walls of the caves in an attempt to crush his traitorous allies. Himiko and Twice avoid it and claim that the biggest weaklings for getting angry so easily. They know Mimic's focus is on them, so the Heroes will have a chance to gather themselves for a counterattack. Deku notices Mimic screaming at the villains, but can't pinpoint his exact location because his voice echoes throughout the cave.
Himiko and Twice safely land and look up to where Mimic is hiding in the cave. Himiko states that weaklings have a desire to show how strong they are, so they look down at others from above. She adds that the Yakuza are very lame and this enrages Mimic. Irate, Mimic screams and gives his location away to Deku. Deku uses a flying One For All: Full Cowl - Shoot Style kick to break the wall and reveal Mimic's hiding spot.
Eraser Head nullifies Mimic's Quirk with a glare and Joi Irinaka falls out of the wall. During his descent, he notices Twice and Himiko waving goodbye to him, taunting him one last time. Mimic curses them both and suddenly gets hit in the face with one of Sir Nighteye's Hyper-Density Seals, knocking him unconscious.
Deku jumps off the cave walls and grabs Mimic in mid-air before he crashes to the ground. He places the defeated villain safely on the ground. After analyzing what just happened, Sir Nighteye surmises that the heroes have been used.