Shihai night he manifested his quirk woke up by falling from the ceiling as his room got lighter
I imagine all around the class 1b dorms there’s connected streaks of black paint on the walls so he can get from place to place in a couple seconds without walking (probably wrote it off as fire safety somehow)
When he was young he couldn’t control his quirk so he couldn’t choose when to go through dark things and instead just fell through. He still does it sometimes and considers it the most embarrassing thing ever. “Even the darkness you have come to know will sink it’s unholy teeth in you,,,”
He likes to sleep in black blankets cause,,,then he is, quite literally, the definition of soft.