Manga where a guy, whose girlfriend passed away/dumped him, is left to take care of a little girl and starts getting too attached
Could it be My Girl?



The guy had a girlfriend who had to travel abroad and she ended up having a kid but didn't tell him, deciding to dump him instead (so as to not burden him with a child). Then she died and the guy ended up taking care of the kid. The little girl is in kindergarten I think, so maybe 5 years old? I can't remember if it was specifically mentioned that the girl looked exactly like her mother, but they're drawn very similarly, and because he is still kind-of in love with his late ex-girlfriend, he decides to take care of the little girl.

There's a total of 44 chapters across 5 volumes. Later in the story, there's a sort-of love interest for the guy, and some drama between the 3 of them.