Let's get one thing out of the way: this manga is absolute trash
Let's start with the plot, or lack thereof. The manga essentially consists of an endless loop with these three steps:
1. Some dude, grandpa or gal underestimates MC since he's so young
2. Some dude, grandpa or gal tries to challenge MC
3. Some dude, grandpa or gal either dies or becomes his lapdog
That's basically it. You needn't actually bother with remembering any of the names, you just need to know whether they admire or hate MC. If it's the former, they just fawn over him. If it's the latter, well, don't expect any tension. There's also some fancy ranking terms and ingredient names being thrown around every now and then, but all you need to know is that MC is getting WOAHSUPEROMEGAUNHEARDOF stronger.
So the characters. Suffice to say, they have about as much personality as the MC does. Aside from Chen's family, every single character introduced either becomes an unrequited love interest, a lapdog or a dead corpse. When MC literally rips apart a few of his enemies, it takes not a single panel for his infatuated females to get over the shock. If that's not fantastic character development, then what is?
And this is why I've read over 100 chapters of this abomination. "Rebirth of the urban immortal cultivator" is like eating a XL bag of chips for dinner. You know it's sh*t, you know it's unhealthy and frankly it makes you feel sh*t. But you still keep on eating.