Rin had rolled his eyes and grumbled around a bit when Yukio had told him to take a bath before bed. At first, he'd figured Yukio wanted him to clean himself out, but it was Sunday night, a strict 'no sex' rule was in place on Sundays.
Rin sat in the bath, nearly nodding off, letting the water sap at his energy and will to move. He managed to turn his head when Yukio walked in though.
"Oh, I get it now." Yukio didn't turn red.
"Shut up." Sitting across from his brother, Yukio tried to relax as well. "I couldn't be bothered waiting any longer." Rin grinned and shuffled closer, leaning his head on Yukio's knee.
"Suuure."
When Yukio didn't respond any further, Rin grabbed his arm and tugged at it. "Turn around." He ordered, pulling Yukio's limbs this way and that until he conceded. Rin pulled Yukio against his chest and nuzzled his shoulder a bit, kissing a mole that happened to be there.
That was enough to give him an idea.
Finding another mole just a little ways down Yukio's arm, Rin moved to kiss that one too, pulling Yukio's arm up so that he could kiss all six of the moles there before switching to the other side. Rin couldn't reach the ones on the front of Yukio's torso, so he continued up his brother's neck, not a mole missed.
The entire time, Yukio attempted to scold him, or whine a bit, but eventually made soft, fond noises. Rin nudged Yukio's face to the side with a hand so that he could get to the moles under Yukio's eye. By now, Yukio really wanted to get out and cover his body with something. There were too many kisses on his skin, too many moles.
Rin leant over Yukio's shoulder in and awkward fashion to reach the mole under his mouth and it wasn't long before it devolved into a sloppy, neck straining kiss. Leaning back against Rin, Yukio tried to swivel a little bit so that it was easier for the both of them.
With one hand on Rin's shoulder, and the other on his thigh, Yukio kissed back twice as forcefully, trying to push him against the bath-tub's ledge. Leaning heavily into his brother's chest, Yukio managed to get his knees to face Rin and the continued to kiss like that for a long while.
Each parting for breathe was punctuated by a smug comment from Rin and each smug comment received another light bite on the lip or tongue. Rin grinned the whole time, arms around Yukio.
God he wished the water hadn't gotten cold.