[old gfycat media embed was here once, but it's now gone]
yooa
Found the performance - its from 2021 K-Pop in Suncheon
From further investigation it seems to be a nipple patch, so close
https://k.kakaocdn.net/dn/p7lQ3/btrjCCf5Vx4/kx0f04ACSiKTJnTkTWlbZ1/img.gif
Look carefully at 10:07 on the right
They deleted the 3rd song that OMG performed bcs they spotted it and there almost no fancams to be found from the 3rd song.
4K fancam from 3rd song but angle is pretty bad (from the side)
Action happens around 1:58 and again around 2:14 and 2:33
There was also one time where Yooa's boob was almost spilling out of ther pyjama top, its from a Vlive and she carefully buttoned up again after some Simps told her in the Livechat - Vlive vod was obviously deleted after that
[MOD EDIT: Dead gofile link removed]
Edit again:
Found the whole Vlive Vod in the depths of reddit
https://mega.nz/file/0LxwjAjC#CstyRbSLvydOBS5PocJuMJOPo2TNbeVUqfmlka-MQrg
It happens at 57:00 , 59:30 they read chat and realize 1:00:00 Mimi makes snippety-snappety signs