What is this anime?

Been looking for a romance anime I saw years back, but can't find it. It was never dubbed. Around 2004-2008ish. Story features all the cliches. Boy comes back home from abroad to attend school. There's the childhood friend who obviously has a crush on him. Then there's the actual love interest, a loner girl with long black hair who lives alone in an apartment. First episode she throws a paper plane out of classroom window and the mc gets it and goes to investigate. Finds her and she decides to kiss him right there to see what kissing is like.