Location: Weiyuan Security Guard Agency
Petitioner: Vice-Director of WSGA
Reward: Token for External Expert, Innerpeace Talisman, Martial Arts Perceptions, Lanling Liquor, Jinchuang Ointment

The first step to triggering this side quest is to find the Weiyuan Security Guard Agency, as it's a little out of the way. You're most likely to find it on your first trip to the southeast, as you're headed to Gusu City from Wudang Sect. Once you've reached Gusu you can find the WSGA along the westbound road, past the Bamboo Forest.

The petitioner for this quest, the Vice-Director, is more or less directly north of the entrance. Speak to him and Yi will (jokingly) ask how to become a guard. The Vice-Director will detail the job of External Expert, which sounds a little more to Yi's liking. If you want you can attempt to join the WSGA... though first you need to survive against the Vice-Director in combat.

Vice-Director of WSGA

The Vice-Director of the WSGA is a standard saber combatant, and all of his attacks are horizontal or vertical straight lines in front of him. This makes him predictable - but also difficult to avoid if he gets in close. There are two ways to end this battle:
  • Beat the Vice-Director up. If you're fighting early in the game this may prove a bit tricky.
  • Survive for ten rounds. Use Lightness to give Yi extra mobility, then just... run. So long as ou stick to the edges of the map it's not too difficult to remain outside the Vice-Director's reach.
After you survive the battle, one way or another, the Vice-Director will give you another task: Get signatures from fellow WSGA members in two distant cities. He'll give you an WSGA Namecard for this purpose.

Your first destination is Pingkang City, which you've likely at least passed by now.  Head north until you see the bridge on your left that leads back to Lotus Lake and Wild Boar Woods, then travel west. Pingkang City is situated next to a bridge. The contact, Chief Guard Wang, is right next to the city's entrance, and he'll give you a Signed Namecard.

Next is Fancheng City. You're less likely to have visited this place, as the main quest doesn't head that direction for a while. Leave Pingkang City and head northwest to Liushan School, across two bridges. Travel west of Liushan School, past Beishan Village, and you'll eventually wind up at Fancheng City. The contact, Chief Guard Jiang, is on your left as you walk south of the entrance.

Backtrack the way you came to the Weiyuan Security Guard Agency. (Alas, this route is the fastest. There are no good shortcuts.) The Vice-Director will send you out on another trip, this time to Xungu Pass, and give you another WSGA Namecard, as well as Martial Arts Perceptions, Confusion Incense, and Two-Times Refined Spirit Pills. Time to set out again.

The Xungu Pass is, at the start of Wandering Sword, locked away. You won't get in until you've started the main quest At Xungu Pass. You have two options:
  • If you haven't begun At Xungu Pass you might as well put this side quest on hold. The main quest will put you inside the city early on, and you can find the contact inside.
  • If you've completed At Xungu Pass you can enter the city. Travel back towards Fancheng City, taking the same route as before (yes, again). This time, though, go north at Beishan Village. There's a thin mountain path ahead, and at the far end you'll find the Xungu Pass. 
Your contact is Chief Guard Chen, and he's hiding in a back alley in the southwest of the Xungu Pass. He'll give you a Letter from Chief Guard Chen as well as the Signed Namecard. Take these back to the Vice-Director to end the quest and receive your reward.