"Sisters" describes what I imagined but was not shown in the movie, the more than 20 years that Du Ledan and Du Leying went through together.
The extra story is from Zhuzi's perspective, involving Yingdan's life in old age, which can be regarded as a complete brainstorming of Yingdan's life.
Intention: They cannot love each other in the secular world, but at least they can still stay together in the secular world.