Working for Zen, Obi, is a strange (but lighthearted mostly) and unusual character in the story. His first appearance is when he tries to frighten Shirayuki by shooting an arrow to a wall next to her. He tends to hide his face under a mask, which makes many people think of him as a bad guy. Out of all the characters in AnS, he is the only character with unknown motives for following Zen so far which makes him a rather mysterious character.
It is later revealed that Obi has feelings for Shirayuki.