|Yukemuri ♡ Hot Spring Strategy|
|Season 1, Episode 6|
|Air date||February 1, 2014|
|Written by||Kazuho Hyodo|
|Directed by||Hiroshi Ikehata|
|Puzzle?! Mystery Appearance of Pretty Girl||Fierce Fighting! Return of Baron Ashura|
Robot Girls Team Z travel to a hot spring town where they meet Lorelai Yoko, an idol from the famous group Rhine X known by her stage name Rhine X1. Her singing causes some strange phenomenon that do not seem to affect her fan Grenda-san. But the only problem isn't her singing but also the Mechanical Beast Girl Belgas V5.
The Robot Girls are at Photonic Hot Springs at an all women's inn where they are relaxing. Their relaxation is interrupted by very high pitched singing. When Z-chan threw a basket thinking it was someone with the Underground Empire, the girl revealed herself. Grenda-san reveals her to be Lorelai Yoko aka Rhine X1 from the legendary idol group Rhine X while explaining it to her friends. Z-chan and Gre-chan didn't know about them and Grenda-san revealed X1 joined after Yae Stroheim left after revealing to have owned a rifle. Lorelai revealed that she didn't really do much and couldn't find work in the city so she opened her resort to sing to her heart's content. Demonstrating her singing caused parts of the resort to be blown away. At meal time, Loreali in her Rhine X1 outfit appeared on stage to sing only to be interrupted by Belgas V5 taking the stage and Baron Ashura and her main robot Mechanical Beast Girls behind her. Belgas steals the stage and performs a song that puts everyone in a trance and makes them act strange. Ashura and her Robot Girls are also affected when they tried to take over the resort. Yoko is depressed that her songs don't make people feel good the same way but Grenda-san who was not affected by Belgas snaps her out of it by repeatedly hitting her. She reminds Yoko that her songs have soul and that it can bring everyone back to their senses. Yoko appears on stage and sings as loud as she can which wrecks the equipment and brings everyone to their senses. Belgas counters with her own destructive voice. However, Grenda-san joins Yoko which causes Mega Belgas to crash in on itself and the make up on Belgas to come off her face. Their horrible singing even causes the surrounding mountains to erupt like volcanos. After this, Yoko and Grenda-san form the idol duo Steel Memories, which surprisiningly becomes very popular.