My thoughts on this PV:
1.Ayu is having fun in this wonderful place with her friends, she thinks this place is perfect but when the fire started, she realized that there is no "perfect" in the world, she didnt want to leave and died in the fire, then the waterfall thing means that shes forgiving herself? I donno...(seem unlikely)
or
2.The whole PV is a dream, she fell asleep in the waterfall and dreamt being on an beautiful island having fun with all her friends,and the fire that happened might symbolize something that broke their friendship, and thats when she wakes up? meh...
or there isnt a deeper meaning at all and I'm just silly
