Source is from their twitter account.
That is just !nokotan@ani.social final form. You can’t trick me
[Art] Christmas Illustration by Mieruko-chan Author Tomoki Izumi
Submitted 1 month ago by wjs018@ani.social to manga@ani.social
https://ani.social/pictrs/image/45d74d0f-a472-458e-993d-49b1ce6bb7ae.webp
earlgrey0@sh.itjust.works 1 month ago
Oh man! It’s so uncanny but the hat is so festive! It embodies the series perfectly. A+