In fact, this irreconcilable conflict was mostly due to Mu Xiangwan's unilateral intolerance towards Su Chaoyang.
Because, although Su Chaoyang was only a year older than her, life's trials had matured him early. Despite her Uncles' good treatment of him, he was still a dependent, so he was grateful and always behaved politely towards Mu Xiangwan, no matter what.
Except when it came to major issues, he would ignore Mu Xiangwan. For instance, if she asked him to steal something or start a fight.
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