From Night Constellations:

Morishita Haruna is a high schooler who has a crush on a guy, called "Haru" (by his friends), whom she always see at the train she rides on. One day, waking up, Haruna was shocked seeing "Haru" sleeping in her bed! Neither one of them knows why is "Haru" there. After introducing to each other, Haruna knew that "Haru" is actually his surname and his full name is Harukawa Kanata. Kanata was just about to leave but an invisible wall on the door prevents him from getting out of Haruna's room. Him being unable to leave, Haruna has no choice but to go to school while Kanata stayed in her room. At the train station, an old man tried to molest Haruna but Kanata saved her?! But this Kanata doesn't know Haruna!! Rushing back home, she saw the Kanata who slept in her room still there! What happened to Kanata's body?