The Failed Swordsman Who Became the Strongest After Spamming the 100 Million Years Button - Chapter 9.2: Black and White Princess and Soul Dress [3] – part 2

A story about a traveler who crossed into a parallel universe, relying on his Proficiency ability to continuously grind experience and become stronger.

I became the Heavenly Demon’s dog.

A boy born with the potential, so great that it threatend the world's powerhouses itself._____Born amidst chaos and tragedy, Azhrael, the son of the legendary Frost King and Celestial Witch, carries a burden no child should bear. Half of his soul was dormant into another world, while the other half was left sealed, hidden from the prying eyes of those who sought to destroy him.He was a child of immense potential—his very existence threatened gods and shook the balance of power in the world.However in the main story, Azhrael was only an “extra.” A mysterious beautiful boy with snow-white hair and dull grey eyes who exists in the shadow of others, bullied and beaten, unaware of the legacy he carries.That Is Until.

He Lang died by his own hands for the sake of his imperial younger brother’s ambition, whom he loved. He was offered to be reborn in exchange for giving up his past romantic feelings. Reborn without the burden of his romantic feelings, he brings with him a manual to new worlds. He wholeheartedly followed the instructions of the manual to complete the tasks, not knowing that the originally slag gong was blackening…
He pleaded to his affectionate Emperor brother to release him, he pleaded to the paranoid prisoner next door, but until the end he remained baffled.
In the end, he discovered that the full name of the manual was – “Slag Shou Cultivating Manual”
Σ (っ ° ° °;) っ!

- Description from Novelupdates