This is Arbu. He's an inu youkai, as if you needed me to tell you that. This guy is a great friend of Yusuke and was an equal sparring rival to Yoko Kurama. He's also loyal to Koenma, (not that he really likes the guy, just he's a dog and loyalty in his natural traits). Arbu's demon power is quite simple, he can and does transform into a very large, dark brown dog. He prefers to battle his enemies on all fours. It doesn't really matter how strong or how powerful the enemy can be, he wouldn't stand much of a chance against Arbu's transformed state. He's what you think a mean, vicious dog should look like.