When her father's company goes bankrupt, Shiina finds out and resolves to sell herself into prostitution by attending high-class parties through an escort agency, in order to help pay off her family's debt.

It is during the first and only such party she attends, where the guests were mainly VIPs and high-profile officials of the Ministry of Finance, and what was set to become an orgy, is suddenly interrupted by a young man wearing an Oni mask, who after giving a speech on how savage and corrupt the upper class of Japan has become, shoots the attendants in order to state his point and then proceeds to brutally slaughter the most prominent guest using a fire axe.

Recognized by a frantic Shiina as Shou, the man simply waves the statement off as a misunderstanding, then grabs the mauled body of his victim and walks calmly to the front lobby, where he is gunned down by police and, before dying, has his head blown off by a device implanted into his own mask.

[2] Akumetsu has generally received positive reviews, with critics praising its intense narrative and social commentary while noting its extreme violence.

[5] Some reviewers have noted that while the manga's complex political themes might not appeal to all readers, it successfully provokes thought and discussion about important societal issues.