The supporting character's harem is very normal - Chapter 476 That person... is Lathel?!

The strong are lonesome. Overcoming the loneliness pushes you to stand invincible at the top.

Pro-disciple of the Shaolin Temple on earth, Huang Xiaolong was reborn into a Martial Spirit world, carrying Hua Xia’s secret knowledge, the Body Metamorphose Scripture. In a Martial Spirit world, only those with Martial Spirit are able to train in battle qi and become a warrior.

Huang Xiaolong born with a heaven-defying rare Martial Spirit was mistakenly taken for common variant Martial Spirit during the awakening ceremony conducted by the tribe and thus sidelined. However, Huang Xiaolong with his common “variant” Martial Spirit again, and again displayed unnatural talent, defeating geniuses, shocking the clan and the entire Martial Spirit World

- Description from novelupdates

Killed by a Sage Emperor and reborn as his 13 year old self, Nie Li was given a second chance at life. A second chance to change everything and save his loved ones and his beloved city. He shall once again battle with the Sage Emperor to avenge his death and those of his beloved . With the vast knowledge of hundred years of life he accumulated in his previous life, wielding the strongest demon spirits, he shall reach the pinnacle of Martial Arts.

After 2000 years has passed, the ruthless demon lord has just been reincarnated! But his aptitude at an academy for nurturing candidates for demon lords is, “Inept”!?