The Irreversible Route, The Land of the Landlord and The Migration of the Sea Blue are a trilogy with the original work as the background, but Shan Zhi has a hidden identity.

A man named Shan Zhi is also very long, but his psychological description of the characters is great.

Heart to heart is not the original background, but the shogunate period, when S was a ninja and Z was a swordsman.

In the modern text of Backlight, ZS is a childhood friend.

Although you said it was original, I strongly recommend the latter two. I have read many ZS articles, but so far I really like only a dozen, so you will never regret reading them!