Ginsei no Proust

Kazuki, the daughter of a wealthy businessman, and a straight-A student at a prestigious school for girls, meets Moka, a wild girl from a rowdy school. What becomes of Kazuki when witnessing a steamy moment between Moka and her boyfriend leaves her all shaken up...?! Find out in this seaside tale of two polar opposites and their fated encounter.

(Source: Manga Plus)