This Hero is Sleeping! - Chapter 7 6: The Mystic Forest

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

Orphaned at ten and betrayed by his guardian at nineteen, the protagonist's life spirals into darkness, yet some light remains, only to be cruelly extinguished when his girlfriend sacrifices herself during a brutal demon attack.As a result, he is bestowed with a mysterious system that imbues him with the strength, making him dedicate himself to eradicating demons.Upon defeating the Demon King, he is granted a reward and chooses to reincarnate into a novel-like world with sealed memories until age thirteen.Reborn as the second son of a Duke, he yearns a peaceful life and respite from his tumultuous past. However, fate has different plans.In a world full of political games and supernatural dangers, he finds himself caught in conflicts involving a transmigrator villain and a regressor protagonist.Amid noble family ties, surprising friendships, and veiled threats, he must find his way through this new life, all the while dealing with lingering scars and the chaos that threatens to engulf him and those around him.Can he truly find solace in a world determined to pull him back into the fight?Will he succeed in forging a relaxed and slow life amidst the relentless anomalies at every step?Read to find out!!

Kanda Kyoichi transmigrated to Konoha and became a temporary instructor at the Ninja Academy. Fortunately, he awakened the Mentor System.By teaching others, he could earn rewards.Thus began Kyoichi’s career as a “teacher” in the ninja world.Shisui: “Sensei’s unique interpretation of the Will of Fire has given the Uchiha Clan a true sense of direction!”Asuma: “The essence of the jade lies in protecting the people, with the advanced leading the way for the less experienced. Only then can Konoha become stronger!”Kakashi: “He’s my life mentor. He transformed Konoha!”...Years later, in the memoirs of Kyoichi, now the Hokage, he wrote:“I honestly just wanted to be a life mentor!”