Weed's dedication towards making money and becoming rich. Unlike most people who would only do so for their own profit and gain, nearly all of the money Weed makes is for his grandmother and sister who he's been taking care of ever since he was a boy and lost both of his parents.
In regards to his sister, even after she's gotten a scholarship and claims she can fund her own school stuff on her own without Lee-Yun's help, he still sets aside an enormous fund for her for anything she wants to buy. How she does repay him? By spending that money he gave her to play Royal Road with him so she can understand him better. Aww.
Lee-Hyun's relationship with sister; they both mean the world to one another and its become quite obvious that one can't function properly without the other.