Books in the Toilet-bound Hanako-kun series

At long last, Hanako-kun reveals his plan to save Nene from her inevitable, swiftly approaching death. But even knowing his intentions, Nene is determined to return to reality—and to do that, she’ll need the help of School Mystery No. 4, Mei Shijima. Can Nene help this spirit overcome her regret and self-loathing and find her way home?!