Shela

Toujou Basara is a high school student whose father has suddenly just remarried. His father then departs overseas leaving Basara with two new beautiful step-sisters. Little does he know, his new sisters, Mio and Maria are actually the new Demon Lord and a succubus!? Almost trapped into a life of servitude, Basara forms a reverse contract by accident and ends up becoming Mio's…

While Basara, Mio, and Yuki have picked up their seemingly ordinary lives, they are attacked by magic-wielding humans when preparing for the upcoming sports event. Basara tries to become stronger by strengthening the testament when Rukia, Maria's sister, suddenly appears. Unknowingly, the war deciding the future of the demon realm has started. Source: ANN