What is the origin of the poem "Vague Thunder" in the movie "The Court of Words and Leaves"?

The thunder is weak and the sky is cloudy, but I hope the storm will come and I can leave you here. There was a faint thunder and a cloudy sky. Even if it doesn't rain, I will stay here.

These two sentences are about love. The first sentence is a girl's point of view, and the second sentence is a boy's point of view. I just want the other party to stay, and the other party has the same intention.

Source: Ye Wan Collection

Makoto Shinkai's film "The Court of Words and Leaves" quoted these two sentences.

Introduction of Ye Wan series

Ye Wan Collection is the earliest Japanese poetry collection, which is actually equivalent to the position of The Book of Songs in China. From the 4th century to the middle of the 8th century, there have been different opinions on the length, date of completion and editors of poetry collections, but most of them are works from Nara period (AD 7 10 ~ 794). It is generally believed that The Collection of Ye Wan was compiled and handed down by many people for many years, and it was completed in the second half of the 8th century by Zhixiong Yakou (7 17 ~ 785). Later, it was revised and approved by several people before it became the current version.

The compilation methods of Ye Wan Collection vary from volume to volume. Some volumes are arranged in chronological order, while others are divided into three categories according to their contents: miscellaneous songs, elegies and songs of mutual listening (in a broad sense, songs that give answers, and in a narrow sense, songs that defend the people (songs that soldiers guard the border).