A Yojijukugo (四字熟語) is a unit of four kanji characters that usually represents an idiomatic saying in Japanese. It is itself a yojijukugo, even though it isn’t idiomatic, since the term can also broadly refer to a non-idiomatic phrase of four characters.

Shunkashūtō (春夏秋冬) is a nice one that means the four seasons of the year, and so is a fourfold written in four kanji characters.

Eshajōri (会者定離) is hopefully appropriate, meaning “every meeting must involve a parting”.

Further Reading:

https://en.wikipedia.org/wiki/Yojijukugo

https://en.wikipedia.org/wiki/Shunkash%C5%ABt%C5%8D

https://www.tofugu.com/japanese/yojijukugo-idioms/

https://www.nippon.com/en/nipponblog/m00111/

https://en.wikipedia.org/wiki/Japanese_proverbs

And these are just interesting:

https://en.wikipedia.org/wiki/List_of_kanji_by_stroke_count

https://gogonihon.com/en/blog/japanese-characters

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