Chu Sang Woo (Korean: 추상우; Japanese: 朱ソウ) is the main character of Semantic Error. Chu attends Hankuk University and is currently studying in the Department of Computer Science. He is referred to as a genius who consistently ranks at the top of his department. Because of his highly introverted nature, he does not participate in social activities. His personality is logical and meticulous, which is how he approaches most situations.