Toraba!

Due often business trips that his parents have in overseas, Shunsuke, who have no siblings, lives mostly alone. But, there always were two people who looked out after him. The kindly widow Ren and her daughter Ai who live next door.

Ren always took care of him when his parents were abroad and Ai, who has been friend with him since childhood, was like a sister to him.
However, as he’s gotten older, Shunsuke starts thinking differently about both girls, and they feel the same about him and thus love triangle between them blooms. Which a girl will Shunsuke eventually choose?

[Adapted from Getchu]