Toilet-bound Hanako-kun, Vol. 5

Nene Yashiro serves as the assistant to the School Mystery Hanako-kun. When
she is invited by enigmatic playboy Natsuhiko to a mysterious tea party, she
meets Hanako-kun's "girlfriend" and his "little brother"...!? On top of that,
she learns that one of the Seven Mysteries is mixed in with her classmates...