The plot revolves around a young girl named Riko who lives in a city that has been built around this massive mysterious abyss. The abyss has many different layers, and the further one goes down the more alien and precarious it gets. Riko's mother was a famous delver into the abyss, but it was believed that her mother was dead. Eventually there is something that happens that could be interpreted as her mother being alive and waiting for her at the bottom of the abyss, so Riko sets off with some friends to try to brave the dangers and make it the bottom.
The main character is of course a loli, and there is also a shota robot with a delicious tummy
. There's not too much that is directly relevant to /abdl/, but there is some evidence of the author's potential fetishes throughout the work even though it's not a fetish manga. For example there's a part where Riko is strung up naked at the beginning, or a part where she is squatting and pooping in the background, wetting herself at night, along with various guro stuff.
Both the manga and anime are great, even if it's not really an /abdl/ thing. Plus it makes normalfags cry about "muh pedos" and "muh Tsukushi is sooo weird!"