Martial King's Retired Life - Chapter 125Book 14:

For three years, Finn Taylor is utterly humiliated. He has endured everything from physical beatings to verbal abuse. For three long years, he has gone by only one identity—the useless matrilocal son-in-law of the Larson family. But this life as he knows it is about to be turned upside-down as he reclaims his position as the head of Peregrine Hall.

On the surface, she’s a gay high school boy. In reality, she’s the hacker known as Z, who hunts criminals on the Internet. A girl dressed in men’s clothes; a master at playing games, punishing evil, and having the highest skill in seducing girls. When people learned that “he” was actually female, the entire population blew up!

A wonder falling down from heaven! A boy possessed by strange blood! Gods tremble! Demons flee! A boy from the land of Dong Zhou. A pink skull as his sworn friend until death. A story of a determined warrior struggling for power. A legend that shakes the galaxy and disturbs the worlds of god, demon and man.

- Description from Novelupdates

The male student, Fukai Nagamasa, ignores his studies for college entrance exams in favor of following the path to chuunibyou. As he fainted during night cramming session before the exams, he realized that he was transported to a parallel world as a feudal lord in the Sengoku Era. Not to mention that suddenly, he was marrying the sixth Demon King, Oda Nobunaga’s little sister, the one who was purported to be an unrivaled beauty?