Location: Peach Blossom Forest
Prerequisite: Complete Leijia Village
Petitioner: Leng Wuqing
Reward: Serpent Awl, Martial Arts Thoughts, Three-Time Refined Meridian Pill

In order to trigger this side quest you must first complete Leijia Village, a mission that ended with one huge, difficult battle. In the wake of that fight Yi and Leng Wuqing retreat to Peach Blossom Forest, and Wuqing will stay here for the time being. Speak to him to trigger Prelude to Counterattack whenever you like.

Wuqing will outline the difficulties facing their investigation, and speak of a possible counterattack. First, however, he wants Yi to return to Leijia Village - alone - and have a look around. Sounds like a bad plan, but okay. Head west of Wuqing's little plateau to exit Peach Blossom Forest, then travel south on the world map to wind up back at Leijia Village.

Once inside Leijia Village Yi will wander around automatically, gathering intel. There's nothing you need to do (besides enjoy seeing Yi's original outfit for a little while). Once he's done in Leijia Village you can trek back to Peach Blossom Forest and speak to Leng Wuqing again. This time he'll send you out to eliminate some pirate scouts... though not too many of them.

Leave Peach Blossom Forest and head west, to Shuanghe Village. There are three spies to root out: 
  • Jian Xi, between the buildings in the north
  • Hao Ren, in the northwest
  • Lu Guo, near the western entrance
All three are pushovers, and by now you can probably wipe them out in a single hit.

Head south once you've defeated the spies. Mount Lian'gu, where part of the previous quest took place, is waiting on your left. Upon entry you'll find Wuqing with two of his fellow detectives. They've set up an ambush on the pirates, and they need Yi to help. You need to assist two battles:
  • The first is to the west, and you'll be helping Qiu Wudao. So long as you stick to the fringes of the battle your team can chip away at the enemy forces while they attack the Liushan School Ironguard and escape unscathed.
  • The second is to the east, and you'll be helping Zhan Wuxing. The same tactics apply here.
Once you've supported the other two battles you can head north, up the mountain, to help Wuqing's squad of men. The battle that follows takes place on two fronts, and you'll have fewer AI helpers - but Wuqing will place himself under your command. You can either focus entirely on one front from the start, or divide your forces and fight both enemy forces at once. The number of Ironguard ensure that you won't be overwhelmed.

After the battle you'll receive the Flame Dragon Dart Advanced Blueprint and Martial Arts Thoughts. Head north from the battlefront to face the leaders.

Lou Fuzhou

Time to bring this war to an end. Lou Fuzhou is quite the opponent, with around 7,000 HP and some powerful attacks. He's also accompanied by four Tianlong Gang Guards, with polearms and sabers, and they're not weaklings either. Lou Fuzhou uses the following attacks:
  • Several line attacks
  • A sparking ranged attack that debuffs defense
  • Immortals' Unforgiving Sword, a forked ranged attack
In addition to Lou Fuzhou's moves, his cronies can Incapacitate your characters.

It may be tempting to try and power through Fuzhou, especially if you outnumber his crew, but you shouldn't ignore the Tianlong Gang Guards. Their ability to Incapacitate your characters can really mess up your offensive. Have one or two characters keep Fuzhou busy while the rest work on the guards. Once they're gone your remaining force can tackle Fuzhou en masse.

You'll gain a large number of items for defeating Lou Fuzhou, likely including the Hawkstrider Sword Stance manual (considering he used it in the battle). And then...

Lou Fuzhou

It was a trick! And... a double trick? Wuqing fights this one alone, but he's much stronger than before. You'll be fine as long as you keep attacking and don't have terrible luck.

Head back to Leijia Village after the battle. Leng Wuqing will disappear once thLe cut scene is done, and you won't be seeing him again until you've dealt with a few things back in the main plot. 'til then, Detective Leng. In the meantime, there's another quest you can undertake to get a new party member: Lou Fuzhou's Ending.