The Ramparts of Ice

Koori no Jouheki

Koyuki Hikawa isn't great with people and always puts up a wall between others. She had been spending her high school days alone, but one day meets the overly friendly Minato Amamiya. The loner, Koyuki, the popular girl, Miki, the guy with no personal space, Minato, and the laid back member of the basketball team, Yota... The story of these four somewhat awkward students in their bloom of youth begins!

(Source: MangaPlaza)