新妹魔王の契約者 [Shinmai Maō no Tesutamento] [The Testament of Sister New Devil]
Kadokawa · 2013–2017 · 9 issues
About the series
A dark fantasy manga series from Kadokawa, The Testament of Sister New Devil ran from 2013 to 2017 across nine issues. The story follows a high school student whose life is upended when his father remarries and brings home two beautiful, demonic stepsisters, thrusting him into a world of supernatural contracts and power struggles. Known for its blend of action, ecchi, and demon lore, the series is most associated with writer Tetsuto Uesu and artist Nekosuke Ōkubo, who brought its provocative premise to life. It matters as a compact, self-contained entry in the harem fantasy genre that garnered a devoted following for its intense battles and risqué dynamics.