
He actually has a forgotten past with the Do brothers about 10 years in the past. The system wiped it out of Woochan's memories to hide their connection because Seohan him with his brother's help.

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Ok, so, Woochan was born with the ability to see the future, usually of people's deaths. As a kid, he revealed his visions without realizing that he saw the future. After people died, Woochan became ostracized as a freak who cursed others.
Later on, in middle school, he got severely beaten up by some bullies. Luckily, Seohan (at the time in elementary school) found Woochan and brought his older brother to help call over an ambulance, during which time he makes a promise to return the favor to Seohan if I recalled properly before passing out.
My guess is that his future sight is actually like the beta version of the system. This is because about a year before the Stardust survival show, Woochan is hospitalized after getting the system status windows, which led him to think that he went insane. The system also blocked some memories of middle school to make him forget his connection with the Do brothers. He does later remember the incident after some things happen.
Oh my, it would nice to recruit this group of merry bandits to Crossroad, especially since my bromance radar is going off between Kailan and Ash.