
Quick answer — Mia Naruse voices Otoha in H2O: Footprints in the Sand, Anri Hiiragi in Happiness!, Mia Clementis in Brighter Than the Dawning Blue.
Mia Naruse voices Otoha (H2O: Footprints in the Sand), Anri Hiiragi (Happiness!), Mia Clementis (Brighter Than the Dawning Blue).
Otoha is voiced in Japanese by Mia Naruse.