Gren is often seen as Iria's older brother and a full fledged hunter. In episode 5 however, it is hinted by Fujikuro that Gren might not be Iria's brother but is possibly her onii-san, (a Japanese term used for both older brothers and close older male figures). He taught Iria much of what she knows about hunting and serves as a mentor for her apprenticeship. He wears a blue cloak and hair beads which are similar to Iria as well as an unusual pendant which is later found by Kei.

(Source: Wikipedia)