From MangaHelpers:
Kousuke has a boring high-school life, but he sits next to his crush--the really popular, cute Tsukahara Meguru, who has a cool, stoic personality. One day, his parents announce that they're moving, but that he'll still be able to attend the same school. The new apartment building has a lovely river and friendly neighbors... and it is next door to where Tsukahara lives! Outside of school, she seems to have a completely different personality, friendly and a little quirky. She makes him promise not to tell the others at school how she acts at home, but why does she put on such an act for her classmates?