A new vtuber from Shigure Ui. Since she take over Ui’s Twitter profile I guess it is Ui’s April Fools take.
Not entirely new, since this 'neglected, unwanted daughter' concept was first born a year or so ago. And since then, spontaneous appearances of Andou Rainbow Johnny Johnny (yes, that's her name) became a thing during streams of Shigure Ui. Still was unexpected for her to completely take over, even for April Fools.