Zest is Aroma's big brother, who helps her run their ranch on Age after their parents pass away. He is far more responsible and calculating than his younger sister. Zest helps further the plot in both Monster Rancher Advance and Monster Rancher Advance 2. In the second game, Holly and Aroma try to set Zest up on a date with Ayase. Aroma even goes so far as to ask Ayase to help them clean their house, and then ducks out on them.
Zest wears glasses and his long brown hair tied back in a ponytail. Although he tries to teach Aroma to be respectful, sometimes he has to scold her.
At one point, Mr. Mardoc offers Zest a job at AGIMA to help them with their money troubles, but realizes he is far too busy keeping up with his sister to take on the position.