Harenchi Gakuen

Harenchi Gakuen summary:

The first ecchi in history.
Initially serialized in Shonen Book briefly before switching to Weekly Shonen Jump. The nature of the content is very extreme with both teachers and students being involved in perverted situations.
Go Nagai would include more extreme content at the encouragement of his editor.
As the manga continued its serialization, it garnered more and more controversy from parents. As a result, the Jump Editorial Dept. decided to cancel the serial.
Nagai, in response to the controversy, decided to end off the manga with the very infamous "Harenchi War" (Shameless War) arc.
*(spoiler)
The arc killed off the majority of the cast in a very gory and disturbing manner and remains a very infamous arc to this day.*
Shameless School is controversial in Japan even today and is regarded as a "traumatic work" by several news publications.
The manga consists of 3 parts, with the last left unfinished due to the cancellation. + last volume includes 3 chapters back story for Hige Gojira.