The singer in this video is Yoyoyochan, a YouTuber who does imitations of other artists. I was following her a couple of years ago and at that time posted
a video of hers, but the algorithm being what it is, she eventually fell off my YT home page and basically I forgot about her. Undeservedly, because she's an excellent singer in her own right.
Here she's singing Fruits Zipper's overexposed "Watashi no Ichiban Kawaii Tokoro," and imitates the members of the group. But at about the 1:45 mark she also imitates Miyamoto Karin, Takeuchi Akari and Suzuki Airi (as well as other artists)! Not sure if she's entirely successful but I still definitely appreciate anybody's efforts at keeping H!P soloists relevant. And she has a fairly substantial following - this video has over 320K views, so kudos to her.