Chivalry of a Failed Knight

Chivalry of a Failed Knight is a light novel series that received an anime adaptation which aired in 2015.

The story is set in a world where there are humans called "Blazers", those who can manipulate their souls to materialize weapons. Ikki Kurogane is a student who is considered the worse among Blazers because his magical power is extremely low, but one day he finds that Stella Vermillion, the princess of the European country "Vermillion" and a top A-Rank Blazer has transferred to his school and is half-dressed in his room. Ikki is challenged to a duel where the loser has to be obedient to the winner for life, but Stella ends up losing the duel. However, they agree to be roommates as Ikki's one and only wish, training together to qualify as the school's representatives for the Seven Star Sword Art festival, an annual tournament held to determine the strongest knight.

Episode 1
Ikki takes his shirt off while listening to the news, and he also attempts to strip as an apology for accidentally walking in on Stella while she's changing in his room. Later, his shirt flies up as he's sleeping, and Stella lifts his shirt up.

Episode 2
Ikki appears with his shirt unbuttoned, and he takes a bath.

Episode 5
Ikki takes Stella and the others to a swimming pool for training.

Episode 9
Ikki strips to his underwear in an attempt to make Stella more at ease so that she can feel comfortable taking off her wet clothes in front of him.

Episode 12
Ikki's clothes are partially torn off in his final match.