They let out a muffled yelp, reflex trying to get them to not fall but failing with his weight added. Frisk ends up sort of lying on their side and his at the same time. Probably better than pinning him against the ground.

"A-Asriel..." Oh, that sounded a lot tinier and sadder than they meant it to. They sniff sharply, trying to stop crying too. That's not helping!