I don't remember exactly, but there's a boy, on his way home and suddenly meet a strange girl, who's eating an ice cream (that's the most clearly part).

Then they move and live in together, alone (it's may seems that the girl is requested to live there to help the boy by his dad, as he's going abroad). Something happen during their living days. At the nearly end, the boy (or maybe the girl) move out. Few years later, they meet again? I don't know. What is this manga name's? Please help

hello! i think it is Anedoki it matches your description

Wow! You're right! Thanks