I Raised A Black Dragon (Web Novel) - Chapter 12: The Guest Stays?

Thousands of years ago, the great abilities of the three teachings of Buddhism, Daoism, and Demonism decided on a place for becoming immortal. Three thousand years ago, a Taoist was close to becoming immortal. Three hundred years ago, the Daqian Dynasty was established, and chaos is expected in another three hundred years. In this era, the path to immortality opens; a celestial swordsman freezes fourteen states with one sword, a heavenly Daoist maiden seeks eternal life, a naturally born Holy Son claims to be invincible, and a Buddhist Holy Monk saves all sentient beings.Gu Wen lives as a beggar, enters a household as a servant, witnessing the disordered world, drifting aimlessly.In a world filled with divine beings, he alone is a mortal.However, a lowly origin is not a disgrace; striving through the grand path, even as a common man and mundane son, he can still be the foremost in the world.“Mortal Gu Wen, my Dao is euqaling the heavens!”

Kurono Maou is a high school student who is sensitive of his sharp eyes and bad expression. No girlfriend but gifted with friends in his own way, he had been living a peaceful life.

The 7-year-old little crybaby met 11-year-old big brother who ran away from home.
[This man became the protector of redemption in his life]

The 16-year-old little dragon fell in love with a 20-year-old big brother.
[It’s a pity that the big brother didn’t recognize him as the little crybaby]

The 23-year-old single father and 27-year-old chief executive meets again.
[This time the little crybaby and his big brother are finally together]

Fortunately we met through hundreds of millions of people, Thank God, for letting us break through many obstacles and get back together again, falling in love with you and being with you again is the greatest fortune in my life.

- Description from Novelupdates

Time travelling from the majestic era after the Recuperation of Reiki, he became Kimura Kazuki, a 16-year-old high school student in Japan, one year before the Reiki Recuperation.

Tentatively, he set out to hone himself to the bone, burning candles at both ends to stockpile resources in preparation for the imminent Recuperation of Reiki. His goal was to be many steps ahead of all humanity when the time comes.

However, it seemed like fate had decided to play a cruel trick on him.

One year later, the Recuperation of Reiki… did not happen as expected.