Age: 25 ("Tokyo Babylon") / 34 ("X")

Last of the Sakurazukamori, the "cherry tree barrow guardians" who use the art of onmyoujutsu for assassination, drawing their power from the bound souls of their victims.

Seishirou may be considered the ultimate product of centuries of breeding: he is the perfect assassin, incredibly powerful and tremendously disciplined, unhampered by emotion of any kind.

Though he possess no real emotions, he is very skilled at their mimicry. During the year of the bet with Subaru, he performed so flawlessly that the lack was never even suspected. He never seemed to be anything other than a kind young veterinarian with an endearing smile and an unfortunate infatuation with Subaru. Perhaps only Hokuto, with her keen intuition, could even fathom that this man would kill Subaru as readily as embrace him, with the same lack of feeling.

Though there is no doubt that Seishirou is capable of killing Subaru, he has spared his life a remarkable number of times. The first was at their initial meeting. The second was at the conclusion of the bet, where he dragged it out long enough to give Subaru's grandmother the chance to intervene. The third was at Nakano Sun Plaza, where he proved himslef still stronger than Subaru, yet let him go once more. Perhaps, unconsciously, he does not truly wish to kill Subaru after all.