After-School Hanako-kun feels a little like a bunch of pieces that might have been intended for the original main series but had to be cut for one reason or another. Several of the vignettes are probably supposed to be versions of standard high school manga/anime episodes like the beach day trip or main character catches a cold and has to stay out of things but is still somehow manages to be part of the story. In fairness, this collection is supposed to be a “behind the scenes” look at what the characters get up to while the main story isn’t going on, and said story takes place at a school mostly during school hours. Main character 1 Hanako-kun is a boy ghost in the role of a traditionally female ghost who haunts the girls bathroom, and main character 2 is Nene a student who gets pulled into Hanako’s world of hijinks/dangerous supernatural stuff.
I did appreciate how the beach episode did not focus on the bathing suits, and the little twist at the end of the Hanako gets a cold episode was mildly amusing. One thread I did notice throughout the whole sequence was the focus on the mokke, little mostly harmless (?) spirits who are obsessed with candy. They show up a lot more than they do in the main storyline and it ends up seeming like someone’s trying too hard with the same punchline of a joke being repeated. There was also a gender swapping episode which seemed pointless, and there is more of a presence of Sakura who is a mysterious vaguely sinister figure in the main storyline and her sidekick Natsuhiko who seems obsessed with her while she either ignores him or has no idea what’s going on around her.
Overall, you need to know the main series to understand this volume, but at the same time it doesn’t add much to the characters or the story.