| Satsuki Hiraga|
平賀サツキ, Hiraga Satsuki
|Kaiju Girl Alias||Alien Pegassa|
|First Appearance||Kaiju Girls Black|
|Voiced by||Yuki Yagi|
Satsuki is a high school student who enrolls in a school located near the Soshigaya-Ohkura station in Tokyo. She is the class representative in the class she enrolls in.
Satsuki has a very complicated family background; her father is a government worker and her mother is a former teacher. Her family is also very strict, forbids her from using the internet and anything that is commonly used nowdays. This is the reason why she didn't know anything else about the kaiju girls other than being the public defenders, as Commander Black found out.
Satsuki is a quiet and honest person, who easily accept anything other people told her to. However, she is very unhappy about the current situation she is currently in due to her family background.
Unlike the original Alien Pegassa, the Dark Zone that Satsuki created is far more powerful, and sucks anything nears it. (This including, but not limited to, people and animals alike) Anything that got into the Dark Zone will remains in that dimension, and can be brought out if a Dark Zone is created.
It is also known that Satsuki will unconsciously create the Dark Zone due to her negative emotion. Furthermore, if the Dark Zone had expanded too much, she won't be able to deactivate it unless she deactivate her kaiju girl transformation using the soulriser.
- Both Satsuki and Izumi are the first case where two different individuals bearing the kaiju soul of a same species.