Back to post some more now, This is MT!Sayu.

A More Trained and Cheerful version of Sayu from Genshin Impact! Still sleeps a lot though...

When a Character I post has "MT!" at the start of their name.

This often means they are either From MagnusTale, Or are affiliated with MagnusTale.

MT!Sayu isn't from MagnusTale Directly, but she is a Member of it now, hence MT!Sayu.

Most MT Characters and a Few others, all have the Face Marks and a Star on their Forehead as well.

The Hair just covers it most of the time...