"The answer is obvious. I refuse. Stop talking nonsense."
It's disgusting how the jerk treats Haruka like an object to place bets on (without her even knowing anything), and I do like that Shinichirou didn't fall for such an immature bait and agree to the "challenge". Funny that in a supposed challenge involving three people only one has agreed, and one doesn't even know anything about it.
I kinda like the fact that he's still competing
without agreeing to the bet. Even if he "loses", nothing happens because he technically didn't agree (neither did Haruka who knows nothing about this juvenile contest). Abusing technicalities is (sadly) also part of the way of adults, and something that hotshot bocchama still hasn't learned yet.
"He's a bastard"
I like his sister. She's not a believer of the "girls love bad boys" stereotype so common in girl-oriented romances. She's also truly doing her part supporting her brother like she said, instead of the typical toxic sibling rivalry (or equally toxic improper infatuation).
Kanako steered her bro away from those loser thoughts about Haruka somehow falling for a jerk like that who's full of nonsense. Why, that's an insult to Haruka, you know? With such thoughts he implied that Haruka was a dumb girl who'd fall for a bastard who only has looks and his parents' money going for him.