No entry in the Monster bestiary.
First thing you'll notice is that Colonel Hyuga, Stat-wise, is a higher-leveled version of Yuri. All you really need to do is fuse and attack. If you can't resist the urge to try out his skill, Revelation, you'll find that Wugui absorbs it. This is true for all special skills.
Uh-oh. Sorry, folks, but you can't win this one. Your spells may as well be Cure, and he uses "Game of Death" too quickly for you to do enough damage with your staff.
Deja-vu, much? Wugui attemps "Game of Death" right off the bat, but it doesn't work! So what do we do? Smack him up a bit, that's what!
You could even take the nostalgic road with Death Emperor, or add insult to injury with Heaven's Fiend. Just don't forget to heal when needed - you're not totally invincible. But since Wugui absorbs all special skills use Yuri's fire fusion monster since he has high attack power and you can increase his attack power with "Fighting Spirit" which in a few turns will take Wugui down.
Wugui's Game of Death move appears to be a reference to the unfinshed Bruce Lee film of the same name.