Is something written on her thigh there?

Zaku_Zelo said:

Is something written on her thigh there?

Yes. It says スッキリ, though from this perspective it's upside down.

It's the name of a series of illustrations by this artist, you can see more by looking at the tag on pixiv: https://www.pixiv.net/tags/%E3%82%B9%E3%83%83%E3%82%AD%E3%83%AA

Or looking at the dic.pixiv entry: https://dic.pixiv.net/a/%E3%82%B9%E3%83%83%E3%82%AD%E3%83%AA

SIJc said:

Yes. It says スッキリ, though from this perspective it's upside down.

......

Dang, I thought it was some version of the artist name (much like the Twitter username that frequently gets added), so I've been tagging illustrations with those with the artist_name + signature tags.