Realmon is Rei Matsuki's partner and daughter to Renamon and Guilmon. In appearance, she is described as being a "chibi-Kyubimon." She is small enough to fit on her partner's shoulder, lacks the

Taijitu symbol on her face, though it does appear elsewhere on her body. The rope around her neck is black and red. The small lines under her eyes are also red and her eyes are golden. She first appears as Rejimon in Book Two and we first saw her as Realmon in Book Five while fetching a soda for her partner while at the hospital. She accompanies her partner during her time-traveling and shares a psychic connection with the girl in a similar fashion to the one between Rika and Renamon.