Oh come on, she's a cute innocent little girl - how bad could it get?
That image has got me curious... Care to share the source, please?
The image doesn't show it, but she's riding a much older girl named Hana, naked, on all fours, with a horse tail plugged into her rear end and a bridle in her mouth, and Katja is periodically whipping her with a riding crop. Even better, she's doing that while calmly discussing business with the two main characters, who are horrified.
It's Ekaterina from Seikon no Qwaser. Dynasty Scans have a doujin on her that's absolutely true to canon.
https://dynasty-scans.com/chapters/my_queen_and_me_training_in_progress
The chapter in Seikon that introduces Katerina ("The Queen and I") starts with Hana. She's the hench-girl to a queen bee that's bullying the protagonist Mafuyu and her gay-for-her best friend. Hana's willing to be a bully because she is insecure about her secrets: first, that she's gay, second that she likes little girls.
Katerina, a grade-school age girl from Russia who is the reincarnated Tzarina Alexandra, has an adult's understanding of the world, and sizes up Hana immediately. Katerina is a dominatrix and a sadist. Hana, despite her tough front, is a submissive and a masochist and becomes her slave. This is from the manga:
(http://2.bp.blogspot.com/-v8UyBSoU0yY/VnU5Fj0iQOI/AAAAAAApccU/71NoJS7-OOw/w1900/9.jpg
Weirdly, they're basically the main love story of a series that's otherwise endless bare breasts and violent action.
I see, thank you. And that sounds like a really funny scene, just from imagining someone doing all that with a straight face, like it's the most normal thing in the world.