Karube is shown to have light blond hair that is shaved. He often has his eyebrows furrowed and is seen wearing his button shirt with a chained necklace most of the time.
Prior to Borderland, he is a high school student who dropped out of school during his early school days. He used to be classmates with both Arisu and Chouta. After dropping out of school, he started working at a pub where Arisu and Chouta often visits to see Karube.