Harry Potter: Ero World - Chapter 143: Core Expansion Ritual! Part-1 ~Light NSFW~

More than ten years later, this sentence gradually spread in Elbaf Continent:

Never use magic to deal with tyrants, because you will find that he will return your spells to you thousands of times after being strengthened by countless magic specialties.

This is the story of a dragon-shaped self-propelled fort that keeps doing things in another world.

There is nothing that one magic can’t fix. If there is, then there are more. ——Izawa

- Description from novelbuddy

He is a firefighter, his face blackened by smoke, coming from the flames, and in one glance, his life was set.The first time he met the young girl, she bent slightly towards him and said, “Sir...”He was amused, thinking she was a little eccentric...She had never seen such a handsome man, tall like a general, and when their eyes met, she was bewildered and forgot she wasn't in the palace...Later, during the school art performance, the young girl sat on stage, dressed in ancient costume, with a veil covering her face, holding a pipa, her eyebrows shy, appearing both delicate and graceful...He raised his alluring eyes, recalling the girl said she knew a little about musical instruments and chess; she was modest.Seeing him in the audience, her heart raced, wanting to perform well but accidentally struck the wrong chord, fortunately unnoticed by him...Later still, the young girl, now grown, suddenly confessed to him, and the usually calm and composed man was caught off guard...It was a love she had hidden deep in her heart for many years, like shards of glass in her palm, both a patient endurance and impulsive agony...The joy of love at first sight, a hidden affection...She would never know that the brother she secretly admired had been waiting for her to grow up...

The strongest Demon Lord dies, and reincarnates as a human. Not only that, he because of various incidents turns into the hero’s best friend.

Follow his journey as he tries to help the hero escape his fate, and on the sideline to conquer the continent while he’s at it.