Sensei, Kiite yo

From Chibi Manga:

Uta thought that her homeroom teacher was a geek, but she saw him when he was dressed differently. Sensei was actually a handsome rock-n-roll singer!? Since Uta had always wanted to have a boyfriend, she threatened him to "go out with her" and she wouldn't tell anyone his secret! but she ends up really falling in love with her teacher..!?

Contains:

? Natsu wa Ginga no Ame ga Furu
Summer Holidays. She didn't want to visit her grandmother, who she is on bad terms with, so she spends O-bon festival alone like she wanted. (Only for watching the house though!) And the person who appears in front of Akari is...!?