There is some infrequent mild comic innuendo/body part humor relating to Reg being anatomically correct. Multiple characters refer to his "penis" and "balls" in brief scenes.

Infrequent nondescript/nonsexual nudity. Riko is sometimes seen partially nude after changing/bathing with her hair covering her chest. Since she is a child, this is presented in a very innocent fashion, though in one scene two characters do get embarrassed by her nakedness.

It is implied in one scene that a young boy becomes aroused sharing a bath with a girl; she asks "What's with your penis?". He gets embarrassed; nothing is seen and the subject is quickly dropped.

At one point, a girl describes her physical examination of a boy in detail. Including that she couldn't see inside his butt, probing him with a measuring stick (which broke), and saying his penis looked like a real one. This is meant to be comical and nothing whatsoever is shown.

As punishment, students are stripped completely naked. Their arms and legs are tied behind their backs, suspending them least 3 to 4 feet off the ground. This is used on Riko early on in the series. Her breasts are covered by her hair.

After a girl gets vomit all over her clothes, and she faints, a boy takes off her clothes to clean them. Her chest is covered by her hair. When the girl wakes up, the boy is embarrassed, but the girl is unblushing.

A boy and girl are both seen naked from a far distance away, bathing in a hot water pool. Nothing is visible, as their legs are underneath the water, and the girl's hair is covering her chest

Two characters are shirtless through most of the show. One is a male. The other is a female. The female lacks nipples and other definitions on her breasts.

A disturbing scene at the beginning of season 2 implies a young character is repeatedly raped.

A boy does mouth-to-mouth CPR to save a girl. No sexual intention

In the manga, there is an implication that two female characters are in a relationship and had sex. However, this is missing from the anime.

Characters frequently go to the bathroom. The main character, Riko, in particular, is shown using the restroom several times. These scenes include flatulence noises. There is no nudity. Just her squatting over a toilet.

In the second season, some monsters lure a girl into a dark alley, where they begin to fondle her under her clothes. They stare at her with longing and breathe heavily. It's a fairly disturbing scene. It's unclear whether they want to sexually violate her or consume her. In the manga, it felt more like they want to eat her. In the anime, it feels more sexual.

An adult man examines a young boy's body against his will. This includes examining the boy's penis. This upsets the boy and makes the man laugh when he finds out the boy is upset.

A character urinates herself while in extreme pain.

There is some occasional moderate fantasy violence, including bloodshed, during fight scenes against creatures in the Abyss.

Some physical violence against children is depicted, which may disturb some viewers. A young girl is slapped across the face so hard that blood drips down from it.

Moderate up until episode 10 in season 1, where it turns severe.

The second season is extraordinarily violent, featuring graphic scenes of murder. The carnage is taken to another level in the second season. It is highly disturbing.

Child violence and torture is a key theme throughout the story. It can be excruciatingly graphic and violent.

One character, a small creature, is violently harmed. To the point that one of their eyes pops out of its sockets, and they suffer from a rectal prolapse. The character survives.

A character rips off their own arm and leg. It is very bloody.

Occasional mild coarse language ('damn', 'hell', 'crap') in the official subtitles.

Some mild crude humor between children, such as references to 'taking a dump' and 'buttholes'. A fantasy creature's fecal matter is briefly seen in one episode.

Some viewers may be disturbed by the overall atmosphere of the Abyss, including the horrific implications of what happens to humans as they ascend.

There is a scene where a character develops a serious medical condition and an attempt at amputation is made. The scene lasts for about five minutes and can be very difficult to watch.

The corpse of a cave raider is seen being eaten by a bird creature. The intenstines are shown being pulled out and when the creature moves, the body is covered with insects that fly away.

The first episode shows an enormous creature that pursues the main character and tries to eat her. Another character is seen bleeding after being attacked by it.

The series takes a noticeable turn for the dark near the end of season 1. This includes full-scale body horror, including widespread mutilation and agonized torture. This starts near the end of season 1, continues through the movie, and is amplified to extreme measures in the second season.

A character experiences disturbing and twisted hallucinations at several points in the series due to taking on the strain of the abyss.

The second season features scenes that are extraordinarily disturbing. Much more so than the first season. Highly intense and extremely volatile to the viewer. This show is not for the faint of heart.

Characters are constantly being mutilated throughout the series. This results in bodies that are hideously, and disturbingly, deformed.