|Affiliation|| Rhine X (Former)|
Photon Power Hot Springs
|Family and Relations||Unknown|
|Voice Actor||Seika Furutani|
|First Appearance||Yukemuri ♡ Hot Spring Strategy|
Yoko is a young woman with short pink hair and green eyes. Her costume based on her namesake features spikes on her red headband and a flash light on top, shoulder pads, armbands, and leg bands. She wears a pink leotard with a face with brown hair on the chest area, over this is a skirt that is extended on the right side. Yoko also wears a necklace with a round accessory.
Yoko is a good natured person, who is generally friendly and polite. She gets upset when someone upstages her but manages to get back after some encouragement.
As a former idol singer, Rhine X1 has a powerful singing voice. However her singing is very high pitched and unrefined; it is so powerful that it blew away her facility, knocked down trees, and even made the water in her hot springs completely evaporate.
Yoko joined the idol group Rhine X after one of their members Yae Stroheim was forced into retirement. However, she did not really get to do much in the group and after she left, could not find work in the city so she opened up her resort to sing wherever she felt like even singing as part of the performance times.
She meets Robot Girls Team Z when they visit her resort and noticed how much Grenda-san was a fan of hers. When Rhine X1 was about to perform, Belgas V5 appeared to steal the spotlight and entrance the audience with her singing. Yoko was depressed about her stage being stolen and the audience being happy by someone else. Grenda-san however snapped her out of it after repeatedly hitting her and encouraged Yoko to sing as Rhine X1. Rhine X1 managed to snap everyone out of their trance but got blasted by Belgas's own high pitched singing. Grenda-san worked with Yoko to counter the attack and defeat Belgas, destroy the resort, and surprisingly form a new popular idol group called Steel Memories.
When the Mycenae Empire attacked, Yoko as Rhine X1 helped the Robot Girls fight them for a while until disappearing for some reason.
- Rhine X1's real name comes from Lorelai Heinrich, the core component of her original counterpart.