A Lull in the Sea

A Lull in the Sea is an original anime series that aired in 2013.

Set in a world where all humans once lived on the ocean floor, a divide came about after many left to follow their desire to live on land. In the present day, the story follows four childhood friends from the ocean who must attend middle school on the surface after their school shuts down.

OP
Hikari's shirt flies up.

Episode 1
Hikari cooks in his underwear, and his shirt flies up.

Episode 3
Hikari's shirt flies up.

Episode 4
Hikari's shirt flies up.

Episode 6
Shun takes his shirt off, and the students take swim class.

Episode 7
Hikari's shirt is damaged.

Episode 8
Hikari wears his damaged shirt.

Episode 13
Hikari and Tsumugu wear happi.

Episode 14
A naked Hikari is found, having not aged a day since disappearing five years ago.

Episode 16
Kaname walks about naked.

Episode 17
Hikari and the others reunite with Kaname as he's putting on some clothes.

Episode 25
Kaname, Hikari and Tsumugu wear happi.

Episode 26
The boys continue wearing happi.