Zero: Black Blood

After explaining the Makai Knights' conduct with human lives when it appears he is planning to kill Iyu, Rei proceeds to fight Ring, who reveals that he left his feather behind on purpose so they can settle this in a battle of both blades and ideals. Even after Ring attempts to have the humans kill him, Rei refuses to stray from his ideals. Yuna and Kain arrive soon after, dealing with the Horrors before they find Iyu. Ultimately, Yuna lacks the will to kill her mother as Iyu uses sings to soothe her. This pacifies the angry mob as Ring finds Iyu singing for her daughter instead of for himself. This causes Ring to assume his true Horror form as ends up falling back into his instincts and devours Iyu after she refuses to sing for him. Once they get the other humans to safety, Rei dons the Zero armor to fight Ring on the back of his Madō Horse Ginga. Once Ring is crippled, Yuna makes her move to make the Horror bleed before being ordered by Zero to sing so they can pacify a healed Ring long enough to destroy him. With Ring no more, Rei tells Yuna that Iyu intentionally allowed Ring to kill her to atone for her actions. Soon after, as Yuna and Kain leave the city, Rei resumes his nightly patrol.