Lunatic Honey

One day, Rise bumps into a little boy named Leo. After she realizes she lost her bento, she searches for it, and Leo had it, so he returns it to her.
After that, she asks him questions and discovers that he doesn't know where he lives, his parents' names, his address, or his phone number. She decides that he has amnesia, so she takes him home and after taking a bath together she read him a story, but she fell asleep. After waking up, she discovers another guy in her room, which turns out to be Leo; older and cockier.