Yi Sang (Hangul: 이상, i-sang) is designated Sinner #1 of Limbus Company's LCB department. Yi Sang is a cryptic and mellow man with a lot of thoughtfulness to him. He was a researcher and architect previously affiliated with the League of Nine Littérateurs, having invented the Mirror as a T Corp. researcher prior to joining Limbus Company. He is the focus character of Canto IV: The Unchanging.
Yi Sang is a man of average build and pale complexion. He has short black hair which frays slightly at its ends, and dead-looking black eyes adorned with heavy eye-bags underneath. He wears the long-sleeved version of the Limbus Company coat around his shoulders, which appears to have been tattered and burnt at the bottom. Underneath his coat is the regular long-sleeved white shirt and red tie, and then a black vest, both of which are tucked into his belt. Written on the left breast of his coat is 'NO.1', and 'YI SANG' on the side. Yi Sang wields a saingeom (사인검, lit. Four-Tiger Sword) in the shape of a dagger kept in a sheath strapped to his left hip. He is confirmed to be left handed. Yi Sang also possess a gray leather notebook labeled '하융' or Ha Yung — as seen on his base E.G.O, Crow's Eye View. The notebook and the dagger are at times visible in various Mirror Worlds.
Yi Sang is a particularly quiet, mellow man. At the beginning of the game, he fails to stand out much among his fellow Sinners due to his tendency to stay silent and watch rather than actively contribute to discussions. When he speaks, his words are often obscure and riddle-like with a monotone delivery, and his expression rarely changes. Though after his canto, he has become to open up a little and even reveal that he is quite naive and awkward despite being a genius.