Wit O'Toole recruited Yoo Chi-won for the Mobile Operations Police. Chi-won's first mission as an MOP was to win a game of capture the flag against the Indian PCs. Before the mission began, Chi-won helped instruct the other new MOP recruits on how to use a Korean altimeter. Chi-won and the unit successfully captured the flag from Major Ketkar. During the escape from the Indian PCs' base, Chi-won and Wit O'Toole let the windows of the stolen car down to shoot oncoming Indian special forces with spider rounds. Chi-won and the other soldiers successfully took the flag to camp, however Wit decided not to brag of the MOPs' victory.
Chi-won participated in a training exercise with the PCs, where he had to help rescue Calinga from extremists. During the mission, Wit O'Toole gave temporary command to Pinetop, who ordered each person to shoot a sniper in the hostage building. The men successfully guessed the location of Calinga based on Chi-won's prediction of where the extremists may hold a hostage. Wit then went on to tell them how they should be able to be successful without technology, so Chi-won was sent back out with the other new recruits to be hunted down in another exercise with only spider round patches to protect them.
A few months later, the MOPs went to Indonesia to deal with the terrorist group known as the Rémesh . During the MOPs' time in Indonesia, Wit O'Toole called the group into a meeting to discuss the possibility of aliens invading Earth. During the meeting, Deen made a joke about most alien clips are bogus, and Chi-won responded with the fact that Deen may spend his free time watching those. Ultimately Chi-won and the other MOPs agreed with Wit that the MOPs should be prepared for the possibility of an alien invasion.
Yoo Chi-won went with all of Wit O'Toole's team to China to fight the Formics, who had landed in southeastern China. On the way towards the Formic lander, the team encountered 6 Formics spraying defoliants. After Wit killed the 6 Formics, a Formic troop transport arrived minutes later, causing a skirmish between the MOPs and the troop carrier. Yoo Chi-won died during the skirmish along with Averbach, Toejack, and Mangul.