Sen & Ryo are minor villains in the video game; Okamiden, which is the sequel of Okami.
Sen resembles a large bird, presumably a crane. He wears a kimono that's somehow merged into his wings.
Ryo is a giant turtle. He wears a robe that somehow is behind his shell.
Both Sen and Ryo are demons that are interested in human souls. Both of them are minions of King Fury. When Chibi started to meddle in their affairs, Sen and Ryo fight Chibi and Kagu.
Boss Battle: Sen
Sen is the first one to fight Chibi and Kagu. Sen fights in a giant puppet known as Renjishi. This puppet uses can use its fists, using wind based attacks, and throwing cogs. After it gets stunned, Chibi slashes at its weaks spots; glowing areas that appear randomly. This causes Sen to fade away, and forcing Ryo to fight Chibi.
Boss Battle: Ryo
After Sen is defeated by Chibi, Ryo takes over in the Renjishi puppet, and does pretty much the same thing as Sen. After Renjishi loses half his health, Ryo grabs Kagu and places her on his shoulder. He warns Chibi tha if he tries to slash Renjishi's weak point it could kill Kagu. So Chibi decided not to hit the weak point, instead Chibi found another weak point, Renjishi's palms. After he's stunned, Chibi rescues Kagu. After aiming at the weakest spots, Ryo disappears.
Boss Battle: Sen & Ryo
Despite both Sen and Ryo being defeated by Chibi and Kagu, both Sen and Ryo reappear, reveal their ultimate puppet, and fuse with their puppet. Just when they are about to kill Kagu, Chibi intercepts the attack barely hanging on. With this act of kindness, Kagu unleashes her true powers. With Kagu's new powers, both her and Chibi are able defeat Sen and Ryo. Kagu then proceeded to perform the dance of exorcism, which purified Sen & Ryo's ultimate puppet, and killing Sen and Ryo. Before they died, they asked someone called King Fury to forgive them.