I enjoyed this a lot! The atmosphere is nice and you've done a good job with the execution as well (in terms of controls and mechanics).
The character feels pretty good to control, if a bit slidey/floaty, especially with the grappling hook. But for the most part, the grappling hook works surprisingly well.
I got to the heart, but I think I may have sequence-breaked my way there, because I reset and only then got the high jump, etc. (This may be because you can essentially scale walls infinitely with grapple-jump combos.)
The story elements were nice and enigmatic, as it seems you've aimed for, and I quite enjoyed talking to the other strange people in the world.
Nice job!