Location: Tancheng City
Prerequisite: See below
Petitioner: None
Reward: Dragon Grappling, Martials Arts Perceptions

In order to trigger this quest you need to complete the four side quests connected to Soulwrecking Song - Overture, which all have something to do with the Beggars' Guild:
Once you've completed these quests, return to Tancheng City. On the way to the Beggars' Guild Headquarters Yi will have an epiphany regarding the case. This will trigger Truth Revealed.

Speak to Li Yuanxing, on the left side of the Beggars' Sect HQ, once Yi has puzzled out a mystery. Yuanxing will tell you to meet him at the inn, and if you go there Yuanxing will tell you to travel to Mount Greenturnip, which is located to the northeast of Tancheng City.

Climb to the northwest on Mount Greenturnip and you'll see Yuanxing standing in a clearing. Approach him to trigger a cut scene. Two more NPCs will show up, and you can speak to them about the whole affair involving Beggars' Sect. Speaking to Xun Yaoyao will boost your Affinity with her, to boot. Talk to Yuanxing once that's settled, then agree to help to trigger another dialogue.

Head back to Beggars' Sect HQ after the conversation and speak to Yuanxing, who has returned to his normal spot. This will trigger the battle that ties up the whole messy affair - or at least the first of the battles.

Yan Weihuan

No longer disguised by a veiled hat, Yan Weihuan will fight at full power this time - and he's much stronger than your last encounter.  Weihuan uses the following attacks:
  • Short-range punches
  • A ranged punch
  • An AOE punch
  • Soaring Dragon, a ranged AOE attack
Your only comrade in this fight is Hou Jiu, a reasonable polearm fighter. Put up as good a fight as you can, but Weihuan will ultimately win - and he's supposed to win. After the first fight you'll be pressed into a second battle, and this time Weihuan will be back up by Xun Yaoyao, who is arguably more powerful. You really won't win this one...

... and, again, winning isn't the point. After the fight Yi will be spirited away to Tianming Village to heal, setting the stage for the final side quest in this sequence: Battle with the Beggars' Sect.