The actual source is a currently ongoing Chinese webcomic by Tanjiu titled "SQ从你的名字开始" (SQ Begin With Your Name), alternatively known in English-speaking circles as "Tamen de Gushi" or "Their Story":
https://weibo.com/1300957955
https://weibo.com/p/100202read8897152
https://www.mangaupdates.com/series.html?id=117186
https://www.amazon.cn/%E5%9B%BE%E4%B9%A6/dp/B015INQPQQ

yat1t just translated this in Korean.

(And it's missing the last page: http://bato.to/reader#e1cf8f53769e2c6a)

I did not know that. Thank you for that information.