"So? We're close."
Those were the words Dawn had said in response to Luca reminding her that he'd still be around the house to observe her walking around with her massive breasts. It was a statement that seemed perfectly fine upon first hearing it, but given their relationship... and the situation... It certainly did seem up for interpretation, didn't it?
"She's your sister, Luca, she's just your sister..." He'd try to repeat to himself in his mind as he'd watch her breasts swell, outgrowing her miniscule training bra, and providing him with perhaps the best view of underboob Luca would ever get to see in his life... if it wasn't attached to his step-sister.
Still, he'd be lying if he said that watching them grow didn't make him at least a bit aroused, especially when paired with seeing Dawn's flushed face afterward. Did... did all that have her aroused too...?
"Wow..." Was all he could bring himself to say, trying to push away the thought that the Chronivac could probably go ahead and make her breasts even bigger than they already were.
"W-Wow is right..." Dawn would reply, her face still red, twinged with a mixture of arousal and embarrassment at being seen by her step-brother like this. "So... I've got my first change... Anything else you'd like to do, big brother?"
"I-I..." Luca found himself speechless before shaking his head, blushing as he got up from his seat. "I-I'm just gonna go use the bathroom real quick...!"
Dawn would giggle as she watched him leave. "Okay, take all the time you need~"
As soon as she was along in Luca's room, she realized that it was just her... and the Chronivac.