It ended for me after we fell off the ravine, new scene loaded in caverns underneat, friend ran off ahead of me and went to black. Is that it so far?
I like it. I just played another dual control platformer like this. I ended up letting my daughter control one though, was fun.
Rain sound bugged. It's a close mic'd sample with very detailed concrete or flat surface splattering. I would opt for a rain loop with no reflective sounds, more of an open field quality ( at least for the duration where you are in that open field) which has air density, but none of the plik-plak'ing your in-game loop does. So the atmosphere was nice, good piano tracks. I would try either footstep sounds or getting your characters some living audio. A grunt for a landed jump, a "hup" for a jump, and a good "whoa!" for those moments that require it (the ground shifting, the big ravine jump, etc) all from randomized pools. Would love to hear some audio from your strange partner, even if it only mystifies his true nature even more.
Good job, would love to see more.