Once Upon A Time, There Was A Spirit Sword Mountain - Chapter 5: Junior Martial Brother's Counterattack

Kaito Nakamura, a shy university nerd, thought he’d found love when the stunning Aiko chose him as her boyfriend. Their sweet, fluffy romance fills his lonely world with hope—until he discovers she’s cheating on him with multiple guys, reveling in the taboo thrill of betraying someone so innocent. Heartbroken and humiliated as explicit photos of her circulate online, Kaito’s tears are interrupted by a mysterious popup: the “Revenge NTR System Beta.” Promising retribution but with a chilling condition — he can’t break up with her.Contains Ntr, read at your own risk

I don’t need any deep relationships. I have no desire for a girlfriend, and I only require one friend who holds any value to me. Ever since I threw out my youth for the sake of efficiency, there is one person who keeps entering the bedroom of Ooboshi Akiteru. She’s neither my little sister nor my friend. She’s nothing more than a bothersome, annoying Kouhai, as well as my friend’s little sister: Kohinata Iroha.

“Senpai, let’s go on a date~! Did you think I’d say that~?”

Rather than blood, it seems like energy drinks run through her veins. She keeps occupying my bed, and she tries her best to seduce me with whatever method she can play to her favor. She’s a girl who’s constantly annoying and obnoxious around me. Even though I’m busy all day long, she doesn’t care.

And in case you’re wondering why all these envious gazes are directed at me, it’s because Iroha is actually really popular. She’s an honor student at our school with top grades to boot, and she’s known for being kind and proper to anyone she meets.

…Hey now, why are you only so annoying when you’re around me?

“Compared to our time, the current generation just aren’t as reliable” they said, “Still, isn’t he the son of the Hero?” How annoying.

It’s been over ten years since the battle between mankind and the demons ended. The children of the heroes who saved the world are all grown up.

One of them, Earth, was a talented man, and everyone expected him to succeed his father as a warrior and defend his country, but Earth was always wary of his father’s title.

One day, Earth is shocked to find his father’s sword, which was used to overthrow the Demon King, sealed in his family’s mansion.

Because trapped within was the ghost of the Great Demon King who was unable to pass on and continued to roam the world.

For some reason, only he could see the spirit of the Demon King, and the Demon King possessed him through the sword.

Every day, forced to coexist with the spirit of the Demon King, they live a strange shared life, when the Demon King whispers to Earth on a whim.

“I have a grudge against your father. If you want to get back at your father and the world, I’ll train you. I’m free.”

Earth receives special personal guidance from the Demon King just to get back at his parents and the world.

Then, in the coming days. The hero’s parents, the heroes of the past, the first love, the princess childhood friend, the geniuses of the era, and the world will tremble.