The Testament of Sister New Devil STORM! Vol. 1 (manga)

High school student Toujo Basara’s life has taken a turn for the strange. When his father suddenly remarries, Basara finds himself with a couple of drop-dead gorgeous step-sisters–who just happen to be members of a demon clan! Naruse Mio is a Demon Lord and Naruse Maria her succubus servant. Chaos and amorous antics ensue as Basara gets acquainted with his new demonic siblings, trying to protect them from deadly demon rivals while struggling to keep up with their lusty, devilish appetites.