Well, wasn't really aiming at seiiyu similarity, but the actual character. Sayuri's character is cheerful, sweet, and caring. Mai's character is calm, timid, and her vocal tone, I guess. When you combine that, along with their facial figure, you get Tohno Minagi. Tohno Minagi has Sayuri's facial figure, personality, and hair, along with Mai's vocal tone and personality (even Mai's blue ribbon).
