I'm Standing on a Million Lives

I'm Standing on a Million Lives is a manga series that received an anime adaptation which aired for two seasons from 2020 to 2021.

Yusuke Yotsuya is an aloof and anti-social student in his final year of middle school who is transported to a game-like alternate world alongside his classmates Iu and Kusue. Tasked with completing quests that increase in difficulty by a mysterious humanoid creature, Yusuke uses his coldness and lack of attachment to others to his advantage, looking at the quests from all possible angles and even toying with the lives of his companions when necessary.

Episode 1
Yusuke appears naked.

Episode 3
Yusuke appears naked, and he briefly weight trains while shirtless.

Episode 4
Yusuke appears naked.

Episode 7
Yusuke appears naked, is shirtless when he finally manages to climb out of the pit, and strips to his underwear in order to save Kahvel.

Episode 12
Yusuke's shirt flies up on two separate occasions.

Episode 24
Yusuke's party is at the beach.