It's been a while, but it I remember correctly, the first part is a heartwarming story about a single guy who ends up adopting a little girl and doing his best to raise her. The second part time skips forward to her in high school, and ends with her becoming lovers with her adopted father (or something like that), which is pretty damn creepy and a nasty shock if you enjoyed the first part innocently. Even worse, it got an anime that only adapted the first part, so anyone who went to the manga to find out what happens next was pretty horrified.