The character in the center, between both Sayos is the personification of Taito's sound group, ZUNTATA.
Taito was the developer and publisher of Kiki Kai Kai, the game the Sayo on the left came from. The Sayo on the right comes from Shikigami no Shiro, published in homeland by Taito. The Sayo on the left also happens to be the actual namesake for the one on the right.

Oh!?
I thought Natsume made Kiki Kaikai.

Natsume developed the SNES port, but the arcade was developed by Taito.