Nemuri Kayama

Midnight, the 18+ only Heroine (18禁ヒーローミッドナイト, Jū-hachi-kin Hīrō Middonaito) is a Pro hero and staff at Yuuei. She was the Chief Referee of the Sports Festival for Year 1.

Appearance
Midnight is a very beautiful woman with long, spiky hair.

Her hero costume is very similar to one of a dominatrix. She has masked eyes, a handcuff on each wrist, a utility belt around her hips, and leather high heels with transparent stockings. The most unique part of the costume is her "shirt", which has a leather-like tie that is connected to the shirt that covers only below her breasts, leaving most of above her torso and arms exposed, but without leaving any of her privates exposed. This is due to wearing super-sheer tights; it is hinted that she originally didn't wear those tights in her debut as a hero.

Personality
Midnight has a very flirty personality, but she also has the tendency to make angry outbursts when someone else interrupts her or when they don't let her finish what she's about to explain and when someone mentions her age. She seems to act on mere whims sometimes as seen when she accepts Mashirao and Shouda request to resign from the the tournament event just because she liked their reasoning.

Ultimate Space & Jams Arc
Midnight appeared along with the other Pro heroes when Class 1-A was attacked by the Villain Alliance.

Sports Festival Arc
At the beginning she tells everyone to play fair during the Sports Festival. The students question her "+18 only" tagline, and ask whether it is fine due to them being in high school. She yells at them and tells them to be silent. She then calls Katsuki Bakugou, the player representative for the Freshman up to the stage. Midnight is then seen explaining the rules of the Human Cavalry Battle and suggested to go for the one that took first place.

Midnight is seen again announcing that they will be doing drawings to determine the pairings for the tournament event and says that before the tournament begins, recreational events will take place first. She then says that the sixteen participants in the tournament event do not have to partake in the recreational events and can abstain from the events if they wish and there is no problem if they want to rest and save their energy. After Mashirao and Shouda request to resign from the tournament event, Midnight, liking their reasonings, accepts their resignations. She then says that the open slots will be filled in by the team that placed fifth: Team Kendou, but Team Kendou decide to give the opportunity to Team Tetsutetsu. Midnight then announces that Tetsutetsu and Ibara will be replacing Mashirao and Shouda. Midnight then shows the pairings for the tournament event.

During the match between Izuku and Shouto, Cementoss contacts and asks her if he can stop the match, saying that Izuku's serious injuries would prevent him from being unable to fight in the next match even if he wins, causing Midnight to think about it and decides to continue the match.

After Shouto is knocked out of bounds and Katsuki angrily grabs him, Midnight knocks Katsuki out with perfume to stop him from doing anything to Shouto.