Kabuto

Original Kabuto

Kabuto can best be described (without big spoilering) as Orochimaru's right hand.

He is a highly skilled Medical Ninja, calculating calmy what the best course of action is and taking any steps necessary to enforce it.

Cold logic, if you might say so.

Currently he takes the role of a "Mini Boss" who terrorizes the Earth Country and needs to be stopped as he develops some kind of superweapon.

It is not essential to stop him, but in the Hall of Fame you can see not only Orochimaru Kills but also Kabuto Kills as a statistic.

Also you get gold and experience, sometimes gems, from defeating him.

He uses his medical ninjutsu in the same manner a player shinobi would.