[ If he didn't know Ianto he'd question the motives behind this, but considering how he's reacted to pain in the past makes it all too easy to believe that this is exactly what he wanted. It's thrilling in an odd sort of way. He's not the one who made the bruises, which gives him permission to mess with them.
Grinning, Spike leans down to trace the curve of Ianto's buttock with his tongue, trailing from the low of his back and down towards his thigh. ]