Kazuho Haneyama/Synopsis

History
When she was younger, Kazuho tried to leap across a river but the ground was wet from rain, so she slipped and fell into the river. On his way to take his hero-course entrance exam, Koichi pulled her out of the water and gave her his silver age All Might hoodie.

Naruhata Vigilantes
Several years later, Kazuho reencounter Koichi while performing his street performances as Pop☆Step. Koichi notes that Pop☆Step is taking a big risk in being a freelance idol since she does not have a permit. A police vehicle is passing by, so Koichi warns Pop☆Step, who decides to end her live performance and flies away.

Later that night, while Koichi was returning home after an incident at work, he meets Kazuho again in an alley. She thanks him for helping her that morning but she make fun of him for being weak and wearing an All Might hoodie, which causes both to start arguing. Pop☆Step begins to leave but bumps into Soga and his friends. The thugs recognize her as the online idol, begin mocking her and even thinking to sexually assault her.

Scared, at first Koichi thinks about leaving her to her fate, but seeing her scared face decides to help her without thinking. He does not have much success at first, and all he gets is to anger even more Soga, but with the sudden appearance of Knuckleduster, between both defeat the thugs and save Kazuho.

After this meeting with Knuckleduster, Koichi becomes his pupil, and the three form the group that would become known not much later as the "Naruhata Vigilantes". Knuckleduster explains to both of them the personal mission in which he is involved: he is trying to dismantle the illegal traffic of a drug known as Trigger, which boost an individual's Quirk, simultaneously weakening their sense of reason.

Although Kazuho does not usually fight directly against the villains, he helps Koichi and Knuckledusters in their patrols, investigating for them, helping to evacuate the passers-by, providing first aid, etc... While continuing performing as street Idol. This makes him get involved in several problems, but also allows him to meet many other people who help him to ascend in the world of entertainment.

One of these people is Makoto Tsukauchi, a senior college student from the same university as Koichi.

Marukane music concert
When Kazuho Haneyama received an email request from her blog that asks her to join a live event on the roof of the Marukane Department Store, she fears that since people view her as a singing street performer and if she screws up they would desert her, yet this is a chance that does not appear often. To help her, Koichi brings Makoto to help with the situation at hand. Kazuho gets mad at Koichi for her knowing her secret identity, to which he replied Makoto has sharp intuition. Makoto promises to Kazuho that she would not mention her masked escapade to anyone.

Kazuho ends up being part of Feather Hats, a musical group composed by her; Feathers, an underground idol duo conformerd by the twins Miu and Yu, the band Mad Hatters and the East Naruhata High Dance Squad; and thanks to Makoto's business skills and contacts, She gets sponsors for Narufest.

The night of the premiere, in the greenroom, Kazuho Haneyama begins to feel nervous about going out on stage. However, a villain causes a blackout and everyone is worry that the show is called off, and Pop☆Step  notices that Koichi Haimawari has gone off somewhere. Koichi emerges from the crowd as The Crawler. He gives Pop her microphone. Pop agrees with the plan for her to go on stage and keep the audience calm.

Pop☆Step explains to the crowd why the power went out, and that the staff are working hard to restore it. She then introduces herself to the audience. Pop instructs those with glow-sticks and assorted light-up goods to line up at the edge of the crowd, and for the rest of the audience to move a bit towards the stage to make a path. She tells the gathering of people that they have time to go to the bathroom before the main event, and that in the mean time she will perform a few songs. Miu & Yu note that she did some slick work on the stage. They also mention that she was as lame as ever, but kind of cute.

When the power is restored. Pop☆Step tells the crowd that the show will begin. The Feather Hats perform their remix of the Marukane Department Store Jingle, and they are greeted with great applause and cheering from the crowd, thats goes wild after the Feather Hats finish their performance.

Kanidoge incident
Thanks to the show, Kazuho's popularity as Pop Step grows a lot, still she continues working as a Vigilante. During the days after the festival, Knuckleduster is increasingly absent, until finally he leaves without saying anything to anyone, leaving his mask and brass knuckles at Koichi's penthouse. Kazuho wonders why Knuckleduster would leave them there since they just parted in town.

Days later, Kazuho is chosen to represent Marukane Department Store in a regional idol collaboration show in Osaka, celebrated on SS Mall in Super Minami. Along the way they meet Fat Gum, who tells them in the address. Later, on the green room for the Mascot Idol Carnival inside the mall, Kazuho is recognized as Pop Step by Monika Kaniyashiki, an idol whose who works for the Kanidoge chain.

After interpreting the theme of Marukane Department Store in the Idol Show, Kazuho and Koichi decide to see the exhibitors and the souvenir shops of the venue. As they walk, they find Monika riding a crab-shaped Mech. That the Kanidoge's uses as walking advertisement. Monika has to leave for some business, and as it takes too long to return, her manager asks Kazuho to handle the mecha.

What they did not know is that Monika is a covert police investigating the illegal traffic of trigger, that used the products of Kanidoge to distribute the drug throughout Japan. Investigating Monika and the police find the main suspect, who activates a code that makes the Kanidoge’s mechas go on a rampage, and takes advantage to destroy all the evidences and escape.

When this happens, Kazuho is now trapped in a rampage mech, unable to free herself or stop the machine. Koichi tries to help her but fails. Fat Gum and Kaniko arrive and chase the mech to stop it. Monika asks Fat Gum to throw her to the mecha, allowing her to use his Super Move Rocket Crab Clip, and the mecha’s legs, preventing it from moving forward.

Monika quickly rescues Kazuho, just when the mecha starts its sequence of self-destruction. Monika, Koichi and Kazuho run as far as possible from the machine before it blows up, warning everyone present to leave. But Kazuho stumbles and Koichi launches to protect her, still too close to the mech. At this moment, Fat Gum appears and jumps to block the explosion of the Mecha, absorbing all the kinetic energy with his Fat Absorption Quirk, saving Koichi and Kazuho's life. He holds enough time for everyone to move away before releasing all the energy, at the cost of his protective fat.

To avoid problems, before they can be questioned by the police, Kazuho and Koichi leave the convention, and sleep on the train on the return trip.