I strongly suspect this is a headshop of Tsumugi on another image. The source is also just someone who is obsessed with Tsumugi, not an artist.

Here are a few other commentaries that seem to all be saying it's a photoshop, as well:

コラ作り始めの時だから色々と下手なコラだけど紬との温泉行ったいい思い出補正でカバーしてる

Source: https://x.com/mugetyu0654/status/1969075815359894007

紬と温泉に入りたい
その想いが限界を突破してなかなかいいコラ画像が完成してしまった

Source: https://x.com/mugetyu0654/status/1600157771445710849

このコラの顔と体の塗りかた違うから違和感あるし誤魔化してみるか

Source: https://x.com/mugetyu0654/status/1624094674666524672