Shadow of the Supreme

Alternative:

天下一品の幼なじみ / 천하제일인의 소꿉친구 / Przyjaciel z dzieciństwa najsilniejszego wojownika / Najlepszy przyjaciel z dzieciństwa na świecie / Друг детства сильнейшего воина / Лучший друг детства на свете / Друг дитинства найсильнішого воїна / Найкращий друг дитинства у світі

Gu Yantian betrayed his family and became part of a demonic sect in the service of the Heavenly Demon. After becoming a sect member, he commits many evil acts against his will and lives a life of regret.

Heavenly Demon’s Great War.
The long and hellish Great War of the Heavenly Demon ended with Wei Xue’er shattering the Heavenly Demon.
Gu Yantian, who had committed atrocities, was captured and tortured by the sect.
As a final act of conscience, he reveals information about the demonic sect to Wei Xue’er, after which he dies after swearing a taboo oath from the Heavenly Demon.

After his death, for some unknown reason, Gu Yantian is transported back in time to the moment when he first met Wei Xue’er.
After realizing that this is not a dream, Gu Yantian decides to lead a quiet life so as not to do anything that he will regret later.
But as if it was bad luck, people from his past life begin to contact him one by one, even though he had no intention of doing so.