Stunt Casting: Played with. The actress who played Ea is an inversion — she was a complete unknown, picked because she was attractive and talented... but mostly because she was willing to stay nude the entire series. It was also a career-killing role, as she apparently did no other roles after Toumei Shoujo Ea. The rest of the cast was fairly well known at the time, both as musicians and as actors/actresses.
The actress who played Ea, Yuki Komachi (credited as UmiMasumi who then went under the moniker of Masumi Kai) had previously appeared in AV (Adult Video) productions. After Toumei Shoujo Ea, she acted in some Direct-to-Video movies before retiring.