1-nen A-gumi no Monster

• Name — 1-nen A-gumi no Monster • Ja Kanji — 1年A組のモンスター • Ja Romaji — 1-Nen A-gumi no Monsutā

• Type — manga • Author — Hideki • Publisher — Ichijinsha • Imprint — Rex Comics • Magazine — Monthly Comic Rex • First — January 27, 2018 • Last — March 27, 2026 • Volumes — 16 1-nen A-gumi no Monster is a Japanese manga series written and illustrated by Hideki. It was serialized in Ichijinsha's Monthly Comic Rex magazine from January 2018 to March 2026.

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.

• Tarō Jimi • Yoshitsugu Matsuoka (PV) • Momo Hananaka • Hikaru Akao (PV) • Tsubaki Yabu • Azumi Waki (PV) • Mari Banri • Chitose Morinaga (PV) • Aoi Tenjiku • Aya Yamane (PV) • Akira Akashi • Masamu Ono (PV)

Written and illustrated by Hideki, 1-nen A-gumi no Monster was serialized in Ichijinsha's Monthly Comic Rex magazine from January 27, 2018 to March 27, 2026. Its chapters were collected into sixteen tankōbon volumes released from June 27, 2018 to May 27, 2026.

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.