Rassei's master. Rassei is very protective of Asia and can easily get jealous when other people, especially men, get close to Asia.
Issei has a profound hatred on Rassei due to him killing the slime he intended to make as his own familiar, attacking him, and getting close to Asia.
Yuuto is shown to have some grudge on Rassei after the latter attacked him twice.
Rassei and Ophis have built a good relationship with each other as shown in Volume 13 where they are shown playing catch with one another. Ophis even offered to train Rassei.