Too late, he already has ideas, squinting down into the dark. "I can move and nothing's broken, that's good enough for now. If someone's hurt they might not be able to tie a rope on themselves." See, it's sensible, a perfectly reasonable request! And one he's happy to argue about if he absolutely needs to, because it's a bad idea for them BOTH to be down here in case something happens. Further sensibility, he takes the time to tie the rope around his middle in case he slips.

Yoichi isn't looking up to see her expression change, but he does hear the urgency in her voice, glancing upwards in time for the betta to rocket past.

Now, he's not stupid. He knows a warning when he hears it, but this wars with the concern that someone might still be down there and in need of help. Surely she wouldn't be that alarmed without good reason, but..

In the end, he doesn't know if the sounds he heard were even people and not say, a wounded predator likely to lash out at whatever happened to be onhand. He hadn't heard a voice, hadn't heard anyone cry out.. After a momentous internal struggle, he turns and begins climbing as quickly as he can, which quite bluntly is neither quickly nor elegantly, he's going to be struggling the entire way.