Shadowverse

Shadowverse is a video game created by Cygames that received an anime adaptation which aired from 2020 to 2021.

The story follows Hiro Ryugasaki, an ordinary middle school student at Tensei Academy. Through a strange occurrence, Hiro obtains a mysterious smartphone with the popular digital card game Shadowverse app installed. Through the game he meets rivals, makes new friends and participates in tournaments, eventually discovering that the true purpose of the game is to save the world from an impending doomsday event.

Episode 13
Hiro and his friends are at the beach.

ED 2
The last button on Hiro's pyjamas is unbuttoned.