@NamelessSoldier: Honestly, I think there's a LOT of layers to it that can piss off Second.
1. That Mein reacted to the new techniques shown by Second not with awe/shock/excitement or anything that show he even care about it, but just 'oh well I lost' like he just think it was something out of his own reach. See Silvia for what Second expects (after he just showed how he instantly learned the skills, her response is to work harder)
2. Because Mein IS 'happy' he lost, because now it means he doesn't have to face his brother. Whereas Second is someone who's only here temporarily and has shown to be very strong anyway.
Even if Second proceed to lose to 1st prince and there's criticism to Mein who lost, it's still better than being humiliated in front of a crowd like the brother planned.
3. Related to #1 but it's Mein's 'loser' attitude of taking defeats as if it's just a natural thing to happen to him, even expecting it (heck, that's why the brother seeded in his own puppet to push Mein up the bracket)