Hey matey, neat little game! I really love the story, and the monster death got me good. The only technical feedback I have is that it was a bit confusing whether you clicked you then the box, or box then you to join stuff. Furthermore, I think this could be a single click, like you click the box, then there's only one character you can click next (depending on whether object is in reality or dream world) so maybe just skip that step to make it simpler?
And getting critical here, I feel like the mechanics could have been deeper, like at the end where you swap to monster, that really only increased the jump height, a very binary thing, why wouldn't you swap to monster? There could be some consequences of each character. And with the coop stuff at the start, it somehow didn't feel coop. Like they were pulling levers for each other, but the characters could probably interact more? Like when the two were joined, I'd guessed I could make one of them float by standing on ground with the other, possibly allowing them to do puzzly things. And this builds upon the connection mechanic, adding some nuance of of how far apart do you want the objects, and how to position them? So I just think the mechanics could've been deeper for more puzzly moments.
Anyways, really nice game, particularly the story beats and art! I believe this was your first jam, so congrats!