osa nazuna (flower knight girl)
Also known as Osanasu, she is Nazuna's younger alter ego handle that comes from the portmanteau of "osanai Nazuna" (lit. child Nazuna), reflecting her much more childish behavior than the regular Nazuna, with higher pitched voice to match.
Appearance wise, she retains her brown hair and large breasts, but her hair are tied into twintails and her see-through skirt is replaced with a miniskirt that kept her panties hidden while exposing her zettai ryouiki.
She makes her debut as a virtual Youtuber on 27th August 2018 (one month after Nazuna's birthday), and addressed Nazuna in the game proper as Onee-chan. Interestingly, she claims to be (probably) 0-years old in her debut video.
Her pre-debut tweets have several short footages at the void realm where Kizuna Ai resides, and the game proper have a promotional SWF animation that depicted a wind-up Nazuna bot ended up being transformed into a child Nazuna.
https://twitter.com/osanazu_FKG
https://www.youtube.com/channel/UC5WJgKelM1YO3AsXtR-t4SQ