Daisuke drew soft circles with his fingertips around his boyfriends belly button. The skin stretched taut over the mass of food that had already been eaten over the course of the evening.
Ken groaned, exhausted and painfully full.
"Come on, You can do a little bit more, I'm not eve half full yet." Daisuke teased him and rubbed his own belly.
Their arrangement was for Daisuke to eat at least as much as Ken would eat whenever he would get stuffed. It was only fair and it had the desirable side effect of at least one of them putting on weight.
It still felt a little unfair to Ken, who couldn't eat nearly as much as Daisuke, but it also helped him push himself to new limits.

It wasn't completely in vain either. He had gotten noticably... not thicker exactly, but less frail looking. But it was hard to maintain. It had taken a couple of weeks of regular feeding for him to pleateau at a skinny, but less boney figure, but it would only take a week of his regular meals, half of which he'd skip or barely even touch if they hadn't been cooked by Daisuke, and he'd go straight back to his old state.
That wouldn't happen again though. Even if there was no effect on him at all, Daisuke wouldn't let up the chance to feed him now that he had licked blood. As much as it had taken them to admit how much they liked it (Ken taking a lot more time and effort to admit it than Daisuke), in the end they were both unwilling to go back to how things were before. Neither could give this up.

While Ken only gained barely enough meat on his bones to not look like he was about to accidentallly disassamble himself, Daisuke got big. His body had no issue putting on all the excess fat. After two weeks he had had the beginnings of love handles and a noticably curvier figure. After a month and a half he had put on enough weight for his belly to spill out in rolls when he sat down and pulled off his shirt. Even eating more than Ken with every one of their just maybe slightly excessive meals, he had more than enough pudge to conceal it almost every time. Not like Ken who's belly felt like it would show a bump whenever he ate more than one tangerine.

Daisuke moved the fork to Ken's mouth and Ken quickly swallowed it down. As full as he was, he wanted to get fuller faster.
They were on dessert by now. A beautiful, rich, heavy, filling cake.
Daisuke stared at his throat as it bulged with every bite he swallowed. Rubbing Kens belly soothingly when he started to groan again. Beneath the stretched skin it felt almost rock hard, something he missed from he very first times he had eaten that much when he was still skinny as well. But he wouldn't go back. He wouldn't give up his new found softness for anything in the world.
And Ken wouldn't want him to either. It may not have been the result they had been looking for, but it was the best side effect imaginable. Having such a soft and pillowy boyfriend drove him crazy in the best way. Just seeing his belly peek out of his shirt when he lifted his arms was enough to give him a heart attack. Holding onto his hips, resting his head on his softness, feeling his belly and his chest poke against his back while he was being held from behind. There was nothing like that.

Daisuke lowered his head against Kens belly, listening to the gargling sounds it emitted and proceeding to pepper small kisses all over it. When Ken grabbed the fork to finally finish his last piece of cake he listened in again, swearing he could hear, or even feel every movement of his throat knowing exactly when the cake entered his stomach and feeling the stomach grumble, complaining furiously. But he knew that as long as Ken wasn't too nauseous, he hadn't hit the limit yet and his stomach could take it. There'd still be some time to push him a little more.