Getting to those areas require getting some boots that allow you to walk in water, to get them, you gotta trade around some stuff with a person you can find in the mountain area.
I'm really glad you're enjoying it and I hope you can complete it!
I just finished the game and AAAA oh my God, it was so cute and wholesome! Gained a special spot on my list of favorite games! And I can't stop listening to the "Thank You For Playing" background music, this SLAPS!