Mr Su’s Tall Tales is a side quest within Bailu. It requires you only speak to him, making this probably one of the most easiest and simplistic side quests in video game history!
In order to trigger it your going to have to advance the story enough to unlock the Sunset Hill area of Bailu, this is where Mr Su resides.
Mr Su is somewhat of a strange guy who holds himself with high praise, you will no doubt realise this when you come to talk to him.
The quest itself will require you to speak to him but in order to progress it you will need to leave and return the next day, this to my knowledge is the only way to advance it.
Do this several times to complete the quest and receive the Caterpillar Fungus as a reward.
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