Metaphorical meaning of 買う Context: in the manga Rikudou, Riku follows his trainer risky instructions in order to win (the trainer had told him to take a lot of punches in order to understand his opponent's fighting style). When, after risking his life, Riku is finally going to land a punch, his opponent thinks: > > > > … > **** What is the meaning of in this case? My guess is that the opponent is envious of Riku's determination end wants to "acquire" it himself by letting him beat him. Is it correct? Here you can see the whole page. Thank you for your help!

sometimes means "to appreciate (someone's trait)", "to value", etc. It has nothing to do with purchasing.

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> 2. to value; to have a high opinion​
> We fully appreciate his excellence as a skier.
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As is the case in your example, it's commonly used in decision-making contexts (e.g., , ). This () also implies the spaker made some decision (apparently "taking Riku's punches intentionally"?)