That's a proper orgasm. The way his legs bend involuntarily and his toes tense up, while his powercontractions kick our that spunk in huge spurts and he can't help but groan with the pleasure. The feelings will be intensified knowing he's being watched too.
Oh wow! That cock just keeps on cumming! Spurt after spurt.... that is clearly a load from a solid edging session. And judging by those grunts and moans that felt fucking amazing. Nothing beats that pure feeling of release