Freshly arrived in hell, rookie damned soul Mimi Kokotsu faces daily trials and tribulations, from being gnawed on to being impaled on spikes. Amidst this, she encounters a smiling woman who seems unfazed by the suffering. Meet Kandata Onee-san, a veteran damned soul with a hellish history spanning five thousand million years, who claims to be "enjoying a slow life in hell." As Mimi Kokotsu learns the enjoyable ways of hell from the slightly naughty yet incredibly kind Onee-san, she embarks on a journey of splattery and sisterly comedic adventures in hell.