The One-Winged Angel has no time to spare on such an inferior white-haired magician with mommy issues - after all, he is the primordial mommy issue person from the Final Fantasy Series! How could Seymour dare to try to take his place? Well, this shall be settled as is proper, in a duel to the death - and Sephiroth is quite equipped to deal with it. With his murderous Shadow Flare to bypass Seymour's better durability and superior sturdiness and offense, Sephiroth won't even break a sweat against this poor one-trick pony.
