The Seven School Mysteries are enough of a staple of anime and manga that most readers have likely encountered them at this point. The human-faced dog, the walking anatomical model, the haunted classroom, and of course, Hanako-san, the little girl ghost in the bathroom, are all familiar tropes of school-set horror and mystery fiction. Likewise the idea of a gender swap of a well-known figure is something we've all seen, although typically that happens to a Sengoku Era warlord or the lead in a romantic comedy. By these rules and all logic, therefore, there really shouldn't be anything all that amazing about Aida Iro's Toilet-Bound Hanako-kun, a manga that relies on both the Seven School Mysteries and switching the gender of a well-known character, but surprisingly enough, this first volume offers a lot more than you might expect.

The story follows Nene Yashiro, a lovelorn high school first-year who seems to fall for one unreachable guy after another. Fed up with her luck, she braves the mystery of the old school building's third floor girls' bathroom, seeking a mystical solution to her problem. What she finds, however, isn't the little girl with bobbed hair and a red dress, but instead a boy about her age in an old-fashioned school uniform – Hanako-kun rather than Hanako-chan. The surprises don't stop there, either: Hanako-kun promptly begins trying to find a non-magical solution to Nene's problems, which annoys her until the end of chapter one, when she realizes that he was actually trying to protect her. Hanako-kun would very much rather find mundane answers for the very simple reason that supernatural ones can rebound on the wisher in unpleasant, and dangerous, ways – as Nene learns to her detriment.

What's more interesting here is the fact that Hanako-kun has also figured out something very important about Nene's wish: she isn't really in love with the boy she wants help winning, nor was she really in love with the first guy she was crushing on before. Nene, like many people her age, is in love with the idea of being in love, and that means that granting her wish might not have made her happy in the long run. Most wish-granting supernatural beings don't give a damn about that sort of thing (or perhaps prefer it, since they don't want to be granting wishes in the first place), but Hanako-kun seems to like Nene enough that he doesn't want that for her. Or, in a more sinister possibility, he sees that she can be of use to him. He says early on in their encounter that this is a job he has to do, and later in the volume reveals that fulfilling his duty as Hanako-kun is his way of doing penance for a murder he supposedly committed when he was alive. Perhaps he thinks that he can use Nene to help him finish his job, playing on her desire to be part of a romantic couple in a way that serves his own ends.

That dark undercurrent is one of the more interesting aspects of this series, even as it indulges in other, happier, genre tropes. A rival character for Hanako-kun appears in the third (of five) chapters in the form of an aspiring exorcist who isn't thrilled with Nene and Hanako's relationship, which makes readers question whether Hanako-kun simply has a crush on Nene and enjoys spending time with her. The fact that he has a knife he can pull from his coat and admits to doing penance for a crime (he never denies the murder charge), as well as the fact that another School Mystery turns out to be the ghost of a teacher murdered in what looks like the Meiji Era, indicates that Kamome Academy may be the site of a purgatory of some sort – and that violence plays a large part in who becomes a School Mystery. (This is particularly interesting when we consider that they coexist alongside actual folkloric beings, like mermaids and fey creatures.) Part of Hanako-kun's job is to maintain the balance between the lore and the reality of the School Mysteries, suggesting that if he fails to do that, something terrible could happen to the students. That Nene might be excepted from this due to her relationship with him just adds another piece to the puzzle.

The art style used for the manga works very well for this juxtaposition between lighthearted school romance/comedy and darker horror themes. The lines err on the side of being thick and heavy, as if painted rather than drawn, and backgrounds are busy with details that may or may not turn out to be significant. (This is especially true of the last two chapters in the book.) Faces are expressive, but we can't always tell what the characters are thinking from them, which works better than you might expect. Pages do tend to be crowded, but the thicker lines that are the default help to keep things sorted for easier reading.

With its mix of story elements and themes and interesting art, Toilet-Bound Hanako-kun is one of the most interesting school manga to come out in recent memory. It still has some quirks to work through (Nene really needs to be a bit quicker on the uptake), but fans of GeGeGe no Kitarō or similar series ought to think about checking this out.