You Can't Escape From Mizudako-Chan! (Manga) Vol 01

Cute, mysterious, and a little bit scary!! Kanisuke Akigai's school life is as ordinary and settled as can be. Tests to pass, girls to feel awkward around, perverted class clowns to bicker with, and a seat by the window, perfect for daydreaming...But dreams may be more than dreams, as Kanisuke's wandering thoughts of rare and interesting demi-humans foretell the coming of a certain eldritch transfer-student cutie, Mizudako-chan--half girl, half octopus, all clingy! Yen Press
(W/A) Megame