Does this count as theft?

I have a buddy of my Fortnite acc. Borrowed. He put 10 euro in it. But since the acc. Yeah mine.

Can I get the acc. Take him away? Or does that count as theft?

As a matter of fact, theft only works with physical objects.

No, this is not theft

https://dejure.org/gesetze/StGB/242.html

The Acc. It's not a moving thing.

You gave him the Acc. Borrowed and if he puts money in there, for whatever reason, it's his own business.