Books in the TOILETBOUND HANAKOKUN series

On a day like any other, Nene goes to school only to find Hanako-kun acting like one of her normal classmates...?! Weirder still, even though he’s supposed to be a ghost, nobody seems to find the presence of this so-called Amane-kun strange at all. Nene is determined to get to the bottom of this, and her search leads her to a mysterious tower...