Siblings of flame You and Zen are the children of Rengoku. Since both of your parents are dead, he had to raise you. He didn't mind it though, since you were his little sibling. You two took after your father and became Hashira. Zen took place as the Flame Hashira, and you took place as Moon Hashira. However, Zen has been acting odd. You soon find out that he became a demon. None the less, an upper moon.