Tonari no Randoseru w

Every day, Yamada Ichirou takes a path to school that crosses with the girl he likes, Fujisaki Shiori. Every day, he thinks that maybe it will be the day he'll have the courage to speak to her. However, hundreds of days have passed and he still hasn't even managed to say one word.

One day, the overly developed 11-year-old Sakura Moe and her mother move in next door to Yamada. While her mother's away, Moe runs over to Yamada's house in a bath towel, demanding that he "rescue" her. Unluckily, that day also happens to be the first day ever that Shiori comes over to Yamada's house on an errand about schoolwork. Now she not only thinks he's a stalker, but also a pedophile! Will Yamada be able to convince her it was all a big misunderstanding or has he lost the girl of his dreams before he even got the courage to say "Hello"?

(Source: MangaHelpers)

Included one-shot:
Volume 1: Ore ga Mahoutsukai ni Naru made no Keii