Nanomancer Reborn - I've Become A Snow Girl? - Chapter 4 - LVL 20

Perhaps it is the choice of fate. As a senior otaku, Qian Lingfeng got the “steel shell system”. However, when he swept the world with the system, became a local rich man, made all kinds of beautiful women, opened a harem, and realized the ultimate fantasy of thousands of otaku, he found that things seemed far from simple!
When the end comes, biochemical zombies suddenly come down, fierce beasts are in power, bloodthirsty zerg roam to kill the world, and human lives are comparable to dirt. Where will weak human beings go in this world? Is humanity going to be extinct? Or … can an otaku save the fate of the human race?

- Description from Novelupdates

One day, a mysterious tower suddenly appeared in the city. The people decided to call it a dungeon, and while it was full of rugged terrain and dangerous monsters, it was also a land of opportunity, where countless treasures awaited. When Sejun, a young man living an ordinary life, is invited to the dungeon by chance, he is thrilled at the prospect of becoming rich, but he is stranded in a hidden area of the mysterious tower. All he has is a few seeds and his body. Now Sejun must farm, collect resources, and figure out his own survival strategy!

After seeking pleasure in the nightclub and a night of romance, he discovered there’s a seed in his stomach;