We Were There(2002)

Bokura ga Ita

Nanami starts high school with high hopes of making lots of friends. She develops a crush on the enigmatic Yano, but he may have too many secrets for her to handle.

At that time...

...I didn't fully understand what Yano meant.

(Source: Viz Media)

Note: Won the Shogakukan Manga Award for shoujo in 2005.