Added Hijikata, since that is who Chen is standing on top of.

Not sure about that black little thing left of Chen. Is that supposed to be Toto-sama? Then that sword fighter with the outstretched hand COULD be Hokusai, but... the swords don't match. Hokusai has two katana and one european sword.
Jeanne Alter Berserker could fit I think, but...

Hokusai has 3 katanas with long handles and one western styled sword. Artist also didn't notice that her katana handles don't have the pommel part, at least in a manner different from the wrappings. Jeanne Alter's handle wraps are supposed to be red so the ones in the art don't perfectly match either one's. Jeanne Alter also wears form fitting gloves while Hokusai wears a bunch of bracelets.

But I'd be surprised if it is Hokusai though. I don't recall Summer Hokusai having any particular synergy with Chen Gong. Jeanne Alter is at least a Berserker which Chen Gong is built to support when he isn't launching ICBMs.