In his room

Mineta closed the door of his room with grand ****, given what a disaster today was: he got the worst score on the pop quiz (a rarity for a genius like him), he was caught trying to spy on the girls in the bathroom again and to complete his luck, some chemicals from a student spilt on him and gave him a brain-splitting migraine.

"What a shitty day" Mineta said sadly and defeated.

His room was full of posters of naked girls on the walls, erotic magazines and various XXX movies. To cheer him up, he masturbated with the magazines, thinking again of his beautiful companions. He entered UA with the dream of being a hero and being surrounded by pretty girls, but it was far from being true since his Quirk was not very powerful, nor did his body help him, being very very small for an 18-year-old boy and everyone in the UA branded him a pervert. And as he rubbed away, he had to admit it wasn't without cause. He still tries to hid his nature when possible. He saw it as natural, but the girls found it repulsive.

"Grrrr... they don't... know what... they're missing - AAAAYYY!"

When he came he had a strong pain in his head which scared him, he quickly went to look in the mirror and discovered that some of his balls were red.

"what... the hell... is my blood get to them? Or is this that BS with the chemicals?"

Carefully he tore one off to observe it, it felt heavier than the purple ones but the size was the same. "Feels heavier, but that doesn't tell me anything... maybe it's an improvement on my Quirk?" Mineta's eyes start to glow with optimism "YES YES, that's EXACTLY what it has to be!" Mineta said enthusiastically.

Without thinking he threw it at the wall hoping for some result and instead of hitting the red ball he bounced like it was rubber. Mineta expected it to explode or something else cool but he just bounced across the room. He caught it and tested it on himself and nothing so he pondered for a long time.

"Okay, well it doesn't do anything on me... my balls normally stick to everything BUT me, so maybe these only bounce?" Mineta sat on his bed, trying to make sense of this. "Maybe it's like Midnight's quirk and it only works on other people?"

He'd have to be discrete, he didn't even know how he made those balls so he thought carefully about who to try it. After a short pondering session, he snapped his fingers on the perfect test.