Jeong-Woo Cha

Jeong-woo Cha is Yeon-woo Cha's younger twin brother. He was one of the strongest and the most famous high-ranker in the Tower before he was betrayed by his teammates leading to the events of the main story.

Jeong-woo was described by Yeon-woo as being a weak and introverted person who liked books, movies, and had a talent of not needing much work to succeed in most things. Furthermore, he also greatly valued his family, even leaving home in order to find a cure for his mother.

(Source: Second Life Ranking wiki)