Impmon is a small humanoid imp creature with a tail and large pointed ears. He wears a pair of red gloves and a matching red bandanna.
At the beginning of Digimon Tamers, Impmon is a trouble making Digimon who spends most of his time picking on humans. He harasses the Tamers and their Digimon (Terriermon later briefly fights back and sends him flying). Impmon seems to dislike humans, saying that no "self-respecting Digimon" would ever ally themselves to one. Later scenes would show that Impmon is in fact the Digimon partner of two children: Ai and Mako. Impmon ran away from the two after they continuously quarreled over him, treating him as if he were a toy.
Impmon resents the Tamers and their Digimon because they, unlike him, are able to digivolve. He tries to prove himself by fighting Indramon, despite Renamon's warnings, but suffers a devastating and painful defeat. Being humiliated and having his ego crushed, Impmon readily accepts the Deva Caturamon's offer. Impmon would gain the ability to digivolve, but, in return, Impmon would have to kill the Tamers and their Digimon. He is very conflicted by this at first, remembering the kindness Guilmon would show Impmon despite his constant insults, but he still accepts, desperate to digivolve.
Impmon is granted the power to become Beelzemon, and blinded by the power, goes down a murderous path. He begins destroying virtually anything that comes in his way, eventually killing Jeri Katou's partner Leomon, triggering a battle that nearly ends in his destruction as retribution for Leomon's death. He is spared at the last moment by Jeri, her reasoning being that while she hated him for what he did, she didn't want to see anymore lives be lost. Shaken by this display and considerably weakened from battle, he wanders off, now guilt-ridden and ashamed of his horrific deeds. He de-digivolves into Impmon again after being attacked by a group of Chrysalimon, whom he allows to attack him because he no longer wanted anything to do with the power that he formerly so reveled in, and is essentially left to die. Luckily, he is found by Renamon and Rika Nonaka, who decide to bring Impmon back into the Real World. After being not only spared, but saved by the people he had once hated and tried to destroy, Impmon eventually resolves to try and make right all the wrongs he'd committed towards others, especially Jeri and the other Tamers.
With new goals in mind, Impmon returns to and reconciles with Ai and Mako, who, to his surprise and joy, not only welcome him back with open arms, but tell him that they will do anything to convince him to stay with them, even stop fighting. Touched by their display, Impmon finally admits (to as much himself, as well as to them) that he loves them. When the D-Reaper finally appears in Shinjuku, Impmon leaves to help the others. Ai and Mako send him their best wishes and a small toy gun, with which he becomes Beelzemon Blast Mode.