The supporting character's harem is very normal - Chapter 461 Karol Magic Academy.

Is Magic really just a wish machine? No! In a universe where Magic truly exists, the ultimate nature of Magic must be as simple and aesthetically pleasing as the laws of physics. This is the story of a mass-produced magical war tool who learned the ultimate nature of Magic. But what of it? Just as birds can fly without understanding aerodynamics, magicians can use Magic without grasping its ultimate nature. Learning the ultimate nature of Magic doesn’t mean the tool can instantly transform into a great magician. But yearning for knowledge is a human instinct, and curiosity is the primary driving force of human civilization. Even for Magic, which should seemingly defy explanation, humans hope to understand its inherent operational laws. The pursuit of Magic’s ultimate nature requires no reason! The story in this book takes place in an era where steel and gunpowder dance together. Here, firearms are on the rise; armor remains the main character; military theory is changing rapidly, with endless innovations in systems and techniques. And this world has something more than ours: Magic. The world is undergoing a profound transformation, and no one can remain detached from it...

One day, a ghost possessed me.

The younger brother donated his kidney to his older brother and chose death over living with only one kidney.

A high school girl tried acting in front of her father.

A Korean military police officer from the Japanese colonial period belatedly tried to protect his country.

A con artist attempted to steal his partner’s heart but ended up losing his own.

I could vividly portray their lives.

Their experiences were akin to a theatrical performance, almost theatrical.

This is a reincarnation/isekai story, about Matt (later TreeTree), an overpowered tree in a fantasy world that serves as the battlefield for an ongoing conflict between demons and the heroes summoned to oppose them.At first a bystander, over a long period of time, TreeTree will learn all sorts of skills, gain levels, and in doing so, build up a forest, train young subordinates, protect a village, and more.