Lily remains unchanged - or does she?

This was all a bit too much for James. His relationship with Lily had always been a little strained - somehow, they just didn't click. And now she outright told him she loved him? Using a pet name, no less? The thing that weirded him out the most was how tingly and giddy it made him feel. But something else was bothering him: His milk had changed him. Quite a lot. So why wasn't Lily affected? She'd drank at least as much as him, even took some right into her womb!

Looking at her face still inches from his own, James stammered meekly: "Uh, L-Lily, you're... you're not changing? Why--?"

"Dunno, maybe I'm immunnngh!" His step-sister began to answer, only to suddenly sit up straight, wrapping both arms around her belly.

"Wh-what's wrong?" James worried, "Are you feeling sick? Did my milk...?"

"N-no, I can drink milk... I'm not feeling sick or--aooww! Anything, it just hurts!"

Lily was almost doubled over in pain, face contorted into a grimace. Staring up at her concerned, James grabbed her upper arms to support her. Sure, they had never been very close, but he couldn't stand seeing a family member suffering.

"Oh shit, I think I--ungh!"

Lily slid off of James, staggering to the door while she was still clutching her tummy. Or... hadn't her hands slipped lower...? James extricated himself from the bed to follow her, the milk- and girlcum-soaked sheets clinging to his skin. Speaking of skin: James only now noticed how smooth and tingly it felt - the small hairs that had been moved by the air with every movement for most of his adolescence seemed to be gone. As for the tingling; it reminded him of the incredible pleasure from when his tits had grown in, but spread out over his whole body.

As he was padding after Lily, he felt said tits jiggle with every step, their sensitive tips bobbing up and down. His teats flopped into his thighs, and the huge, fluffy ears on both sides of his head bounced up and down, slapping into his jaw gently. It felt strangely pleasurable, having all his most sensitive parts jostled around like that, but still, this would take some getting used to. With his center of gravity having shifted considerably, James was unable to keep up with Lily, even stumbling once in the hallway, barely able to keep himself from falling by using the wall to support himself.

This gave Lily more than enough time to reach her room and lock herself in, leaving James stuck outside. All he could do was press his enlarged, drooping ear against the wood of the door - flattening his tits against it as they were much too large not to get in the way - and try to make out what was happening to his step-sister.