Weak Hero X M!Reader

Yo, to whoever unfortunate soul who reads this, here's your summary.

M/n Park, the older brother (by two years) of Ben Park. He's always been a prodigy but that never created any conflict within the family. They were quite proud of their first son/brother.
M/n exelled in his studies, so much that when he was 15, he was offered to be promoted with the others to high school. Afterwards, he graduated from high school at 17 (yes, I know it's unrealistic) and decided to start his own company.
Two years later, his company is know to be on par with Donald Na's and is thriving. Basically, ya boy is filthy rich (don't worry, you donate thousands yearly. Not for reputation but for the actual purpose.)
He and Donald are somewhat close, not considered friends though.
However, how did that change when M/n found out that Donald caused his little brother's injury?