A large bus carrying students from Ryoreikan High School, attended by children from respectable families, plunged into an accident. The bus ended up at the scene of a yakuza conflict.
While the students managed to survive, when they regain consciousness, it is the yakuza who were supposed to have died in the accident that end up inhabiting their bodies.

Eiji Shiokawa, a member of the Tsukihiro syndicate, awakens as "Shiori Kirino" and tries to blend into school life for the time being. However, suspicious incidents begin to occur in the surroundings... With the appearance of a refined young lady but the soul of a yakuza, a never-before-seen "conflict" unfolds on the stage of an ultra-refined girls' school!

(Source: Hakusensha, translated)