Sakaki "Tornado" Makio (Nagase Tomoya), the tough 27 year-old wakagashira (young master) of the Kantou Sharp Fang family loves alcohol, fighting, women and pudding. However, he is a high school drop-out and by academic standards, pretty dumb. He is illiterate, extremely bad at math and cannot even fully write his name in kanji. His father (Ichimura Masachika), who is also the family's oyabun (boss), worries for the future of his son and his organization as he wishes for Makio to succeed him. He decides to force his son to return to high school to receive his diploma. He asks an old friend who happens to be the principal (Iwaki Koichi) of a nearby school to admit Makio. If Makio doesn't graduate, the position of boss will be given to his younger brother Mikio (Kikawada Masaya).
Furthermore, he must pose as a 17 year-old during school hours and in the presence of any classmates or teachers outside of school. If his cover is blown, it would be the end of his high school career as well as his hopes to become boss. Things start out rough and tough as Makio's violent temper is tested. As the lessons and days go by he learns there is much more to school than just tests and studying.
Tanaka Koki plays Makio's loyal shatei (younger brother), Kashii Yu his attractive teacher, Tegoshi Yuya, Aragaki Yui and Murakawa Eri are his supportive classmates and Osugi Ren his wise senior lieutenant.