Shadowverse

In terms of style, GG or BlazeBlue would be a better fit.

Less than SC, in my opinion.

This is most likely an advertisement.

Probably. And Street Fighter likes to insert its characters everywhere. In Online Dogma, there were costumes based on him, which was also very out of place. And then costumes based on him appeared in Persona 5. But in the original game, there wasn't anything like that; there was only a more or less appropriate crossover with the source of inspiration, "Berserk!"