Deimos no Hanayome: Ran no Kumikyoku

悪魔あくまの花嫁はなよめ 蘭らんの組曲くみきょく

Two siblings were happy on Mt. Olympus, until they fell in love. Deimo's sister Venus got imprisoned in the Swamp of Death. To save Venus's life, he must find a human reincarnation so that they can continue their love.