Sang Yi is an alternate version of Yi Sang, a Sinner of Limbus Company with the employee no. 1. He was the first possible universe Yi Sang saw when he first made the glass window, which allowed him to see the possibilities of other universes. He is mild, level-headed, & somewhat mysterious and enigmatic. His expression doesn't shift much, only slightly. Cares for others in his own way. The glass window/the mirror is the only way to communicate with him due to him belonging to another universe