"We kill all vampires. We share our own fallen ‘blood’ and use it as a weapon...!"

The Arbitration Knight Order, which travels around the world to keep the peace. Rinslet, who has just become a regular knight, meets Yuri, a vampire girl with cool silver hair and crimson eyes. She kills her own kind by manipulating the power of her ‘blood suit’, which materialises blood into swords, bows and arrows, but Rinslet knows that she is an abomination, and her feelings for her are mutual. She becomes Yuri's kin in exchange for her life, and her goal is...?