The Testament of Sister New Devil

Step‑siblings, demonic bloodlines, and a hero’s oath collide in a chaotic battle for a twisted family.

When Basara Toujou’s father drags home two gorgeous girls as his new step‑siblings, the teenage heir’s first encounter with them ends in an embarrassingly awkward bathroom clash. The red‑haired Mio and the petite silver‑mane Maria quickly prove they’re far from ordinary high schoolers—Mio is the heir to a fallen Demon Lord, and Maria is her loyal succubus attendant. Their arrival thrusts Basara back into the shadowy world he tried to leave behind: a secret war between heroic bloodlines and demonic forces. Revealing his own lineage as a former Hero, Basara is forced to juggle a precarious alliance with the very monsters his ancestors hunted. He signs a master‑servant pact with Mio, vowing to shield her from both the relentless Heroic Council and the ravenous demons that still roam the night. As battles erupt and forbidden desires surface, Basara must confront a lingering darkness within himself that threatens to consume everything he’s come to protect. The series blends high‑octane supernatural combat with a heavy dose of fan‑service, all while exploring the uneasy bonds that form when family is chosen rather than given.

A battle-harem series where the plot exists largely to stage uncensored sexual encounters between the male lead and his demon step-sisters, including a magical contract that forces intimate acts. Expect near-constant fanservice, graphic nudity, and themes of coercion framed as romance.