After a few hours, there's a soft rustling and a dimming of the light as Marten unties the little bows holding up the curtain. Then he slips inside and curls up on the same pillow as Fives' head. By combination of coincidence, gravity, and Fives' adamant choice to keep his back turned, the warm little lump of Marten's body slides down a bit so that he's nestled against the back of Fives' neck.