Star Gate - Chapter 286: Silver Moon’s Reaction (I)

High school student Mikoshiba Ryouma was summoned to a different world in the middle of a war. Sensing the malice from the one who summoned him (a summoner of the O’ltormea empire), he uses his martial arts to run away, killing important people of the empire during his escape. After the escape, he rescues two twin sisters from the hands of thieves. The sisters who can use magic, swear to serve him as subordinates. Thus, Ryouma begins his journey on the path of the supreme ruler.

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

- Description from Novelupdates

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

Rex was an ordinary salaryman, resigned to a dull life of monotony in a towering megacity. But his world shatters when he’s conscripted by Nexum Dynamics, a ruthless megacorporation, and thrust into a brutal war for a barren, alien world. The planet holds unimaginable riches, but it’s also swarming with the Krhyssari, an insectoid race that dominates the surface with their hive-mind precision and relentless aggression. Amid the carnage, Rex had an extraordinary encounter with Cleo, an ancient AI, a survivor of a long-extinct civilization. Cleo isn’t just an artificial intelligence; she’s a consciousness imbued with memories of her people’s interstellar empire and equipped with advanced bio-nanotechnology. Offering Rex a new purpose and unmatched power, she transforms his fragile human body into a hybrid of living metal and flesh, making him the ultimate weapon. But Cleo is more than a tool of war. As she journeys alongside Rex, her cold, logical algorithms evolve, shaped by his humanity. Together, they form a bond that transcends the boundaries of man and machine, discovering love in the midst of chaos. As Rex and Cleo fight for survival, they uncover a shared ambition, to rise as intergalactic overlords, uniting or conquering the galaxy.