Eternal Equinox is a story about a boy named Ryuuki Samejima who is a prince of the Kyoto region, of Japan. His father Daigo Samejima the feudal lord along with his Mother Sakura and his little brother were killed during the day of the Equinox. In the deep darkness, a bright red crimson shining upon the whole castle of the Edo was the blood of the royal family with the older brother Ryuuki holding a sword in his hand upon his parent's corpses.