Cass blinked, out of breath and in a haze of emotions and sensations he couldn't quite make sense of anything, though he realised it didn't matter, because every word that Percy somehow miraculously managed to say wasn't less true because of that. He knew that in his heart - had known that long before he said it, and felt his stomach flutter at that one word. Forever.
A deep loud groan escaped him as Percy thrust hard into him and he couldn't for the life of him catch his breath as he felt every muscle in his body tense and release as Percy brushed his prostate like that, come spilling all over both their stomachs as his body shook with pleasure, his arse clenching harder around Percy.
'I don't want anything less than forever,' he managed to pant into Percy's mouth, promising himself to be more eloquent when he wasn't so completely overpowered with pleasure.