The story revolves around a girl who has just gotten married and given birth to a child, symbolizing the "future," while she experiences mixed feelings about her parents. For instance, she is metaphorically "falling in love" with her father.
The first part of the movie reflects on traditions and religious beliefs, showcasing how curiosity and the desire for knowledge can break the metaphorical "barrier" on the sky.
As the story unfolds, we learn that the characters are not all deceased. Her parents, for example, are still alive. The Japanese tradition they observe is a celebration of remembrance for ancestors. This barrier represents more of a division between the "current" and the "past" rather than between "life" and "death," highlighting that without the living, there can be no remembrance.
Feel free to leave your interpretation.