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He has saved the life of another noble family who is loyal to the emperor, and he has found the company of several malcontents who have a score to settle with the general.
I think this can provide a basis for your working to fight the Yellow Turbans especially if we are with Liu Bei (who started life as a simple weaver) The story goes that during the Yellow Turbans rebellion, Liu Bei was a Judicial Officer but was forced to retire after beating a corrupt official.
That could be a start for your characters (and his company of malcontents)desicion to fight with Liu Bei to restore order to the Empire...
PS in my description it notes that Ch Pa-Chieh also spent a few years as a 'bandit' and so perhaps he could be one of the malcontents with whom you kept company (ie Chu Pa-Chieh and Gau Xuan know each other from our days in the city underground.