The supporting character's harem is very normal - Chapter 101 Successful Flexing

The leader of the thousand demons, the Demon God Chun YeoWoon. Due to an unfortunate accident, he had been sent to the distant future.

The mortal body, metamorphosis, longevity, immortality, and eternal life. These five realms, step by step, reveal themselves in front of you. As a normal person, how can one try step by step to reach and open the door to eternal life?

Between the heaven and the earth lies the mortal body, the mysteries of metamorphosis, freedom of longevity, the power of immortality, and the hope of eternal life. A story filled with endless new magic, a new world of immortal styles, people, demons, gods, fairies, magic, kings and emperors. A world of love and hatred, revenge, and mystical battle, all in “Eternal Life.”

- Description from Novelupdates

Wait right there!!! You stopped?! Good. Now, read below. I know what you guys are here for, so let me make it clear from the beginning, this novel has everything you want to see, like... Milfs, Virgins, Netori, No Yuri, Act of keeping the bloodline pure, Oyakodon, Succubus, Vampires, Elves, Queens in the harem, Princesses, Gilfs, Demonesses, Angels, Goddesses, Dragons, Phoenixes, Dryads, long seggs scenes, Dual cultivation, Cultivation, System, Yandere, Overpowered MC, and many more. This was something for the more cultured people, but besides these, this novel also has... wanna guess what is it? Hmm...?! Yep, you got it! A good story, that won’t make you feel bored, if you don’t quit in the beginning that is. It has many plot twists and many new concepts that you won’t see in any other novel.

“Heaven's Taboo Doggy Technique”Living his life as a cripple, Xuan never expected anything good in his life; however, the day he discovered a secret library in his sect, he was able to walk into a parallel world.A different world, a modern world of cultivators and his world.The library of taboo techniques awaits Xuan again: the milking technique, doggy technique, dual technique, or sword art technique—every technique in one library.He can now use every technique to boost his cultivation above the gods themselves. Goddesses want his immortal white juice, mothers want his body renew techniques, step-siblings want his meat raw. Xuan's body was the pinnacle of taboo in both worlds.The fucker of mothers, stripper of daughters, and the founder of all techniques—it was only a matter of time.