He looks up at you with wide eyes and nods quickly. "Of course... I mean, nobody would believe me anyway... but still, it's our secret." His cheeks flush as he thinks about what just happened, and he can't help but feel a sense of closeness to you now that you've shared this experience together. "Thank you, big bro..."
He reaches down, rubbing at the spot where your cock was only moments ago, smearing some of your cum across his ass.