I love this picture, but who is that man under Komachi?

Youmu's grandfather probably.

That's Maat, an npc from final fantasy XI.

Much like Zeid (to the left of Parsee).

The other non-touhous seem to be generic player characters from their armor, along with buront who could easily fall into that category anyway.

There's Jin Fu-Ha (that random guy from AOF who, memetically, hangs around that dirty ninja and Parsee) being physically abused by those three mischievous fairies.

I like the blue and white outfit Parsee got going here...

This is a Square Enix x Touhou Crossover