Princess Kakyuu Cast List
Here are the actress who played Princess Kakyuu:

Yoshioka Sakoto
Yoshioka Sakoto as Princess Kakyuu and Out of Costume Profile:
First Name: Sakoto
Last Name: Yoshioka
Birth date: April 20
Blood Type: O
Good With: Singing, Acting, Dancing
# of Myu Performances: 49

More Information:
Sakoto on Site [offical site, Japanese]

She played Princess Kakyuu in both Eien Densetsu and Eien Densetsu Kaiteiban The Final First Stage!!. As Princess Kakyuu, she was operatic and graceful.

Following myu she has been very busy acting on stage in multiple shows.

Musicals in:
Eien Densetsu
Eien Densetsu Final Act [kaiteiban], Final First Stage

Toyama Ai
Toyama Ai Out of Costume and as Princess Kakyuu Profile:
First Name: Ai
Last Name: Toyama
Birth date: March 3, 1973
Blood Type: A
Good With: Singing, Acting
# of Myu performances: 21


More Information:

Ai played Princess Kakyuu in one musical only, Kakyuu-Ouhi Kourin The Second Stage Final.

I haven't found any information on Ai following her myu days.

Musicals in:
Kakyuu-Ouhi Kourin