High-schooler Hiro Hiyorimi dies pushing a young woman clear of falling construction beams, only to be revived as a servant in her honor guard. The woman is Hime, a daughter of the Monster King, and his new half-living life binds him to her household alongside the android maid Flandre. Hiro is pulled into Hime's fight against the siblings who keep sending vampires, werewolves, and other monsters after her in a contest over the royal succession.