Kayin almost squeaked in disbelief at the knowledge Toriel had been secluding herself for weeks, but manages to keep his composure. When Toriel asks to get a good look at him, Kayin places himself in front of the tent flap so she had an unobstructed view, giving a small wave and a friendly smile, even as his eyes held a bit of worry and concern in equal amounts.
"Of course." Kayin replied, eyes briefly flitting to Asriel, before stepping forward and into the tent. He didn't bat an eye at how the inside seemed a bit bigger than the outside, and had no trouble sitting upon the corner of the bed as he rubbed the back of his head sheepishly.
"Well, when I first woke up in Alphys's lab a little bit ago, and figured out where I was, I would have said the question to ask would be
when I was from, but uh, things are different enough here that where is important too." Pulling his phone out, he found a large family photo that included his Grandmother and Grandfather, standing behind and towering over the rest of them. He floated his phone over as he said,
"First though, I should introduce myself. I'm Kayin S. T. Dreemurr. And uh, I'm from a different future."
Spoiler (click to show/hide):
https://www.furaffinity.net/view/41127090/
Asriel, Boss Monster Chara, and Azmerelda. I don't have a ref for Frisk yet in my Alt Universe