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.

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.