Disguised As A Boy To Attend Belmont High School - Chapter 12: The Threat

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.

A good-for-nothing man married a beautiful girl but was kicked off the bed on the wedding night. Furiously, he wrote a bill of divorce and ran away.
He was schemed a car accident in which he nearly lost his life. However, it turned out to be a blessing. He swallowed the soul that passed through the outer world, thus obtained superb medical skills and martial arts.
Later on, with the silver needles and invincible martial arts, he embarked on the road of counterattacks and was committed to his great dreams.

- Description from Novelupdates

In chaotic times, one seeks survival; in prosperous times, one seeks fame.Despite being weathered by the vicissitudes of life, the Great Yu Dynasty still found itself in an era of prosperity.In the northwest, a youth trekked nine thousand miles on foot, slaying the Great Demon alone to compete for a lifetime of glory.In Long Lake, an unmatched Grandmaster hurried to the mortal realm to establish a sect, leaving his name to be revered for a hundred generations.In the imperial capital, a saintly figure spread his teachings far and wide, with followers throughout Qingzhou, his legacy lasting forever.Yet within Qingzhou City, in the compound of a family with a long military heritage,there was a child who never engaged in serious pursuits, instead spending his days playing chess, painting, fishing, and playing the zither.Years later—……When the sword rose, dragon smoke stretched for three thousand miles, and a single strike wiped out the cities of nine provinces!Among all the laws of the world, only I, have entered the path.