is a Japanese manga series written and illustrated by Hideki. It began serialization in Ichijinsha's Monthly Comic Rex magazine in January 2018.
At Suezono Girls' High School, Class 1-A is infamous for driving away homeroom teachers through bullying, blackmail, and manipulation, earning the nickname the "Monster Class." A new teacher, Taro Jimi, is assigned to the class despite its reputation. Although he appears plain and unremarkable, Jimi takes a strict and methodical approach to teaching and discipline, refusing to be intimidated by the students.
The class is led by Momo Hananaka, a popular and manipulative student who attempts to force Jimi out like the previous teachers, including trying to frame him in a scandal. However, Jimi remains unfazed and begins systematically confronting the students' behavior and personal issues. Jimi's own mysterious and troubled past is gradually revealed, with his methods beginning to change the class.
Written and illustrated by Hideki, 1-nen A-gumi no Monster began serialization in Ichijinsha's Monthly Comic Rex magazine on January 27, 2018. Its chapters have been collected into fifteen tankà Âbon volumes as of September 2025.
In commemoration of the release of the series' third volume on July 27, 2019, a promotional video was released on Ichijinsha's YouTube channel that same day.