Kazama Shoto's actual partner Digimon is Zephagamon, but he used MedievalDukemon in the Digimon Liberator webcomic. The other illustrated "Digimon" in the back is Mother D-Reaper from Digimon Tamers, who has a card in the Digimon Card Game, which has a really high DP count and is unaffected by any effects of the opponent, but cannot attack at all. A certain Shoto card (EX7-064) gives your own Digimon some keywords, the important one being blocker and combined with Mother D-Reaper, it gives you a low cost, high DP blocker consistently, which cannot be interacted with.
A believable explanation would be that human ears are functional ones (ear canal and such), while animal ears are vestigial (no ear canal, but still have nerve endings and can emote, they just are flaps of skin).
