Seishi is a miracle existence. Born sometime before or during the Warring States Period, he was supposed to have died in the Second Shinobi World War. However, someone saved him and gave him telomerase-creating cells, most likely the work of a Haru Clan member. Seishi, who has seen too much bloodshed, has been trying to kill himself for decades but any injury he sustains heals just as it opens. After 12 decades, Seishi carved a scar on his chest to show that he is cursed and vowed to stay alive to see how the Shinobi World will turn out.