I've no idea if this has been talked about here or elsewhere but decided to link it here anyway. This actually would explain alot and I'm fascinated by it, I like the idea.
I'm not 100% behind all what this dude is saying like Ichiji having dragon DNA in him. Wasn't his "Spark Red" for exlosions rather than fire and flames? Obviosuly if I'm wrong, correct me, and if I'm wrong then the following makes no sense ^^
But instead of dragon in him, I think Ichiji has more something like Bombardier Beetle or Mantis Shrimp in him. Bombardier beetle would be rather obvious but I'm honestly more excited about mantis shrimp. Ihciji showed in last chapter that he can land fast punches and mantis shrimps punches have acceleration of 0.22 caliber bullet, and they even create heat and light.
As for Yonji, I have no other idea for his animal than spiders or silkworms. has he even showed his Winching?