It was actually nice, i didn't expect that this game will be so touching. In my interpretation these two girls have a really messy relationship depending on one another thus making each other's lives unbearable. The mushroom thing is a way to become some sort of symbiotic being, it's the only way they won't hurt one another and the only way to continue their depending realationship. Or smth like that, idk i'm sleepy and it's not my native language...