Set in the frontier region of Alpas, the novel follows freelance mercenary Leroy Schwarzer, who is asked by Rena, an assassin he has known for years, to rescue her sister. When he enters the assassin organization Crimson Despair, he encounters its tiger-like leader, who calls him a fellow comrade.

For some reason, he calls Leroy a fellow comrade.

About a century after darkness became poisonous, children affected by it stop growing and gain superhuman powers, only to be shunned by society. Amabashi Iwai, one of those children, accepts a job protecting the prostitute Base and is drawn into a mounting threat from unidentified creatures.

In a world of children adapted to darkness, a protection job opens the way to an unknown threat.

Niken Yojimbo is a sword-fighting fantasy centered on Kigino Ishizumi, a bodyguard who wields two blades. While protecting his client Hinagiku, he confronts his companion Sakujiri and deadly shinobi, and comes to face both his swordsmanship and his way of life.

A bodyguard carrying two swords faces his strongest foe to protect the people entrusted to him.