This game looks very polished! I would love to try playing this game but unfortunately the online function was taking too long for me to find another player to play with. So I'm basing this review based off some youtube gameplay, and I'll do my best to translate my thoughts of just observation alone:
1) The walking sounds are funny and adds to the charm - I'm going to just say it first. It's so cute and amazing. I love it. It's like tiny singing voices. (I still hear them in my head)
2) Co-op/multiplayer games are largely determined by possible interactions that can be done between players (the best co-op games arguably are tabletop where everything affects everyone as a result) - and from here, there is a healthy amount of interaction from the puzzle design and the interactions between players.
Some notable things I particularly like and I think contributes is how you can jump on top of one another - but also walk pass through each other. I think this just makes it easy to manuever around each other without bumping and stuff. Very nice attention to game design in being very particular with how you handle player-to-player interactions, I admire you skills in this!
3) I think this is highly subjective territory but I'm generally unsure on the rewind aspect of your game - which I assume is the teleport back to your soul. I can agree that it does add to the puzzle aspect of the games but its quite loosely connected to the rewind theme.
Nevertheless, a loose connection is better than no connection - especially for such a smooth, polished game - I still enjoy (watching) it!
4) You have good priorities set, focusing only on primarily pretty much 3 mechanics : buttons and respective gates, rewinding to souls, jumping on one another - to create a few levels and using the rest of the time to fine-tune/polish these mechanics that will go to round up your game.
5) Your cartoonish art direction adds to the charm, refer to part 1. Kudos man.
I don't think there are much cons to list - if anything, I only wished there were more levels! If this ends up becoming a bigger game, naturally you'd want to introduce more puzzle elements, voice chat system.. etc etc. That will certainly make this a big project. I very much like how you approach this theme, very unique and very strong to your identity.
Looking forward to more from you and hey - if you did decide to expand on this, I'd want to follow it and maybe try looking for an online partner again!
Cheerios.