A Night-Child, made by Ravena in the late 1400s. He was a Samurai once, and deeply devoted to his daiymo (feudal lord). Caught up in the Ōnin War before the Edo period, Seishirou obeyed orders to protect his lord until the very end, and almost died for it.
Ravena, who’d been haunting the island of Japan for a while, found his loyalty fascinating, and decided to make him her own personal assassin.
Later, in the mid 1600s, Ravena found and kidnapped Jonathan. She believed that Seishirou’s cold-hearted willingness to obey made him the perfect person to keep track of her pet project. As it turned out, that combination also doomed him.