A short time ago when Sir Nighteye's group began infiltrating the Shie Hassaikai's Headquarters, Ryuko Tatsuma's group was fighting Rikiya Katsukame of the Eight Bullets, whose Quirk allows him to absorb a target's vitality by touching and inhaling and allows him to grow larger. They eventually managed to overpower Rikiya and knock him unconscious.
Ryukyu orders the Police Force to continue restraining Rikiya while Nejire Hado, Ochaco Uraraka and Tsuyu Asui prepare to head after Sir Nighteye's group. Suddenly, Ochaco and Tsuyu along with the Police Force become tired due to Rikiya inhaling their vitality, much to Ryukyu's surprise since she thought she knocked him out. Conscious, Rikiya reveals that the drug he took is kicking in which has enhanced his Quirk and now he can absorb a target's vitality simply by inhaling.
Now larger and stronger than before, Rikiya attacks the Police Force only for Ryukyu to take them to safety. 20 minutes pass and Ryukyu's group is in a standstill against the rejuvenated Rikiya. Nejire decides to take action and attacks Rikiya with her Quirk, which allows her to convert her own vitality into pure energy and emit shockwaves, although Rikiya manages to block her attack. When Rikiya's drug wears off, he demands Nejire to let him touch her, to which Nejire vehemently refuses.
Suddenly, Izuku Midoriya appears and states that he called reinforcements and that their objective is underneath a nearby crossroad. With this information, Ryukyu hatches a plan, transforms into her dragon form, and charges at Rikiya. Ryukyu drags Rikiya to the crossroads and commands Ochaco to make them float and Tsuyu to help drag them towards the crossroad.
With Ryukyu and Rikiya's bodies now weightless, Tsuyu drags them to the crossroad with her tongue. At the crossroad, Ryukyu orders Nejire to blast her and Rikiya onto the ground with everything she has. Ochaco releases her Quirk's effect and Nejire blasts Ryukyu and Rikiya with her Quirk. The combined weight of Ryukyu and Rikiya along with the force of Nejire's shockwave is enough to make the crossroad collapse, causing Ryukyu's group along with Rikiya to fall down into the Shie Hassaikai's underground where they land in the middle of the battle between Izuku and Kai Chisaki.
Izuku is surprised with Ryukyu's group suddenly appearing while Ochaco and Tsuyu are shocked that the Izuku they saw above was fake. Himiko Toga, Jin Bubaigawara, and a copied version of Atsuhiro Sako are above ground; in the underground, they let the copy out, then Jin made copies of himself to dig a hole to the surface where Toga transformed into Izuku to trick Ryukyu's group. Jin is glad that the Heroes showed up today as it allowed them to identify the "core" of Chisaki's operation which is Eri and they plan to snatch her.
Jin orders the Atsuhiro copy to go and snatch Eri. Atsuhiro goes to snatch Eri which surprises Ryukyu's group. Izuku tells Ochaco that he is leaving Sir Nighteye to her as he goes to rescue Eri. However, Chisaki prevents Izuku from reaching her with a rock pillar and he grabs her. Chisaki is annoyed with everything being ruined and seeing the hole, an opportunity of escape, prepares his escape by reconstructing a large and long rock pillar to take him to the surface.
Izuku refuses to let Chisaki get away. As they head for the surface, Mirio Togata's cape caught by debris, which Chisaki finds sickening. By instinct, Eri grabs Mirio's cape after remembering Mirio's kinds words.
Suddenly, Eri begins emitting a strange energy which starts affecting Chisaki. Eri is revealed to be the granddaughter of the original Shie Hassaikai's boss, whose daughter cut ties with them after a dispute over her marriage. Another factor that caused the boss's daughter to disassociate from the group is that Eri caused her father's death after he touched her and he simply vanished into thin air.
The Shie Hassaikai's boss reveals to Chisaki that Eri has a strange Quirk that did not resemble anything from her family lineage and believes it is a genetic mutation. The boss does not know much about how Eri's unique Quirk works but due to it resembling Chisaki's Quirk is the reason why he has asked him to take care of Eri and investigate her Quirk.
During an investigation, Chisaki starts thinking that Eri's Quirk is on a completely different level from his restoring or repairing and hypothesizes that Eri's unique Quirk can rewind genetics; Chisaki finds Eri's Quirk to be terrifying.
In the present as according to his hypothesis on Eri's Quirk, Eri's Quirk begins activating which causes Chisaki and Shin Nemoto to split apart, returning Chisaki and Shin to normal. Today was the first time Eri tried to escape but had given up hope due to thinking there was no escape from Chisaki. Robbed of her freedom, experiments were made on her body day in and day out.
Eri's fearsome Quirk caused her to blame herself her being born with this strange Quirk and resigned to being "cursed", accepting her fate. However, Mirio's words shook Eri's heart to the core and could no't bear to see others hurt for her sake; she was further shocked that they refused to give up on her, which caused her to start developing new feeling, the feeling of needing to be saved, which allowed her to activate her Quirk's power.
Izuku grabs Mirio's cape which Eri is also holding onto.