Yume Utsutsu no Hana no Sono

Rem, an occult-loving virgin boy, finds himself attracted to his friendly classmate, the gal Himawari. However, Rem discovers that Himawari is caught in an "astral projection" and can't return to her body. To make her soul return from the astral projection back into her physical body, it seems Rem must make her "climax"...!? (Source: Yanmaga, translated)