Life is Easier If You're Handsome - Chapter 159

A broken man who ended his own life finds himself reincarnated into the game he used to play. However, instead of becoming the protagonist or a powerful antagonist, fate places him in the role of a minor villain—a mere stepping stone for the protagonist in the game's first arc.

A Federation Colonel with abnormal thoughts was locked in a dark room and met a little looney.

“Your whole body emits a scent that I dread (covet) and fear (desire).”

A frigid Colonel X little looney roommate: A sweet story of interstellar travel

- Description from Novelupdates

An Individual from Earth finds themselves in the Shinobi World, equipped with a Scientific System. From that moment, he delved into scientific research far ahead of its time.

Allen, an eight-year-old boy from a poor family in the royal capital, is living a poor but happy life together with his mother. One day, however, memories of his previous life suddenly come back to him and he remembers that he is in an dating sim game and that the capital will be destroyed by war if he doesn’t do something about it. If this continues, both he and his mother will be killed! With a sense of urgency, he decides to rise to the occasion in order to save his precious mother’s life and save his favorite character, the villainous young lady Anastasia, the only girl he liked in the game, from her all too tragic and ruinous end. This is the story of a man who isn’t even a character in the game, but who strives with his steely determination and uses all the knowledge he has to turn overcome fate!