Quick answer — Makiko Nabei voices Ren Seto in My Bride is a Mermaid, Chihaya Senou in Kamisama Dolls.
Makiko Nabei voices Ren Seto (My Bride is a Mermaid), Chihaya Senou (Kamisama Dolls).
Ren Seto is voiced in Japanese by Makiko Nabei.