Kazuo Iyoda

After the events of the TV series, the 18 year old Yoko Godai has abandoned her special agent Saki Asamiya name to return to her normal life, and is now studying for college entrance exams. However, she accidentally bumps into a young man named Kazuo Hagiwara trying to escape from a group of hitmen, and learns that he comes from Sanko Academy, a private school located in a remote island known as Hell's Castle. The school is ruled by a former revolutionary thought to be dead named Hattori who is trying to brainwash students into terrorists to help him stage a fascist coup d'etat in Japan.

Sencond entry in the duology.

Shingo Kusaka, the illegitimate brother of KUSAKA Group chairman Shunichiro Kusaka, is framed and sentenced to death by his own bloodline. Surviving the brink of death, Shingo erases his past and is reborn as a professional assassin—only to find himself hunted by an unknown enemy.

First entry in the duology

Five-dollar hitman Mayo and KUSAKA Group chairman Shunichiro Kusaka are half-brothers living in completely different worlds. When the underworld Matsuri Clan plots to seize control of the KUSAKA Group, the long-feuding brothers find themselves facing a common enemy.