...1000 yen.
Why would his sister resent him though, I wonder? For taking away her chance at a boyfriend, or something?
Well hey, that could easily transition into a different kind of scenario, so there shouldn't be any problem.
He was going to ask her out but the brother said she liked someone and the guy took it as she likes someone else instead of him. tho what the brother meant is that his sister likes flower guy. thus causing the guy to stop trying to go for her.