The supporting character's harem is very normal - Chapter 454 Lathel returns.

Childhood sweethearts.
The most popular person in school is my childhood sweetheart.

- Description from Novelupdates

The moment Kazuma arrived in the world of Jujutsu Kaisen, a cursed spirit knocked on his door, making him panic.Fortunately, he awakened the mission selection system.[Mission Option 1: Look into Gojo Satoru's eyes for ten seconds.Reward: Mangekyo Sharingan][Mission Option 2: Change Mei Mei's hairstyle to twin ponytails and have an in-depth communication with her~Reward: Tsukuyomi!]During the Shibuya Incident, Sukuna went crazy.Chibaku Tensei, Infinite Tsukuyomi, Susanoo...Yuji: “I thought that Gojo-sensei was already invincible. I didn't expect Kazuma to be even stronger than him.”Since he had arrived in this world, Kazuma vowed to make a happy ending.Gojo becoming Go/jo? That won't happen in his presence.Yuki, Nanami, Mai, Junpei...?He's going to save all of them.***This is just a translation. All credit goes to the original writers.Raw: 咒回：人生选择，开局万花筒！

“Did you know? I was once the most powerful person in the world, undefeatable even by the gods. If only I can retrieve my body, I could resurrect once again.”“So what?”“So... who has hidden my corpse!”

Dual cultivation and apocalypse—words that mix like oil and water. There's nothing charming about seducing feral women on the road.

However, when Kaze Lexicon, the emperor of the Immortal Plane, got transmigrated into the past, he refused to give up his debaucherous ways—apocalypse or otherwise.

Armed with the knowledge of the future and an encyclopedia of overpowered cultivation techniques, he immediately set forth to obtain resources and build a lavish settlement to live a comfortable life dual cultivating in the apocalypse.

However, while it's obscenely protected and powerful, he finds himself in another predicament. The cultivators farming humans for their war, and the desperate humans, become enemies far more dangerous than the zombies and monsters that afflict humanity.

Join Kaze as he rebuilds his reputation from a bullied weeb, obtains wealth, builds power, starts a faction, makes lemonade, trains his people, protects his past lovers, conquers settlements, and fights humans, monsters, and cultivators, all for the sake of two obscene goals: enjoying life and building an army of engineers to bring modern technology to the higher planes.