No sex but characters wear short skirts and revealing swimwear

A boy's grandparents mention the death of his mother.

This show features lots of violence and gore. Teenage students, teachers, and other adults are killed in horrific ways. Most deaths are caused by chance and the environment. In the TV version, violent scenes are censored by dark circles, but the censoring still allows some gore to be seen. The death scenes are explicit, graphic, and frightening.

Blood, or blood-like substance is seen spread out in the opening animation.

In the English dub, there are 2 uses of "Fuck", once used as the last dialogue in episode 10 ("...I f*cked up") and the other is the same line as a recap in episode 11. There are also 6 uses of "Shit", with the occasional uses of "Damn" and "Hell" throughout the rest of the show.

In one scene, an adult is seen smoking a cigarette in front of students.

By the looks of the cover it's going to be scary.

This series is very dark. It has a mysterious ambient and dark themes. The intense scenes don't come by surprise, so, there are no jumpscares in this show. Some strong scenes are offscreen too, but they are minimal. However, there can be just one intense scene in an episode or so, and the rest of the episode is not frightening at all, just with the mysterious ambient. Perhaps, the death scenes are shocking and disturbing. People sensitive to blood, gore and bizarre deaths should stay away from this Anime.