WMG / WATATEN!: an Angel Flew Down to Me

The play in the final episode is an allegory for Hana and Miyako's relationship.

It's basically the premise of the show and also how the manga is gonna end: A human falls in love at first sight with an angel that flew down to her, but because they can't be together in their current state the angel goes through a Mountain of Time so they can reciprocate each other feelings. The tragically big time skip with the grandma and her sister dying is an excuse to have one of them play a different character wearing a wig with Miyako's hair (which is the closest thing to have Miyako herself in the role of the human) and have this human end together with the angel, Hana.