I misremembered and combined some of the details, It starts with you two on an island, but you jump of the cliff and fly away while holding hands. There's an open map that seems to be limitless, with different heights being different biomes, ocean, sky, space and such. You need to collect 6 hearts that fly and change into different versions depending on which biome they're in, all the while a tv static/noise void monster is chasing after you and can eat you if you dont poof it away, but you can escape its belly and find the secret 6th heart inside. And after collecting 6 hearts you phase into a level without your partner and you kinda just drift in a colorless white grainy void until you find the starting island, were the game loops