Invicinble Colorless Butler - Chapter 30 - The Princesses Situation Part 1

Two heroes of the game Legend of Heroes 2 who were rotten waters*.

Childhood sweethearts.
The most popular person in school is my childhood sweetheart.

- Description from Novelupdates

Son of a bitch! I just finished this godawful fantasy novel, and now I'm knee-deep in it – as David, the disgraced son of the Solarian Empire's top general! Talk about some twisted cosmic joke. But hold on a damn minute... maybe this isn't all bad. Armed with the knowledge of that trashy plot, I can become the ultimate shadow player, an overlord perhaps. Screw the damsel-in-distress harem too – it's time to pull the strings and become the real power behind the throne. This isekai might be a steaming pile, but I'm rewriting the ending with a little more... Debauchery (wink wink).

Unhindered in the Demon Domain, the king is solitary!

In the world where immortals and demons strive, a good natured fellow sought the Demon Dao in search of justice.

At the end of his journey, he had eventually become this generation’s Heavenly Demon Emperor.

Although I am not fond of slaughter, I do not dislike it!

Desiring to see the Demon World, this is how I strive, this is how I become the Peerless Demonic Lord!

- Description from Novelupdates