Gu Zhen Ren
Hmm, so far, so good. It seem that this mc will actually act like an old man and not like a hormone-driven teenager despite being hundreds of years old. Something that disgusts me is when the mc has the setting of being either hundreds of years old, thousands of years old or even a million years old or more, but he acts exactly like any other mc, an emotion and hormone driven wreck that isn't mature in any way and doesn't seem to be older than his physical age in the least. Where the "super old in past life" setting is just there to let him get a lot of plot armor knowledge and "experience", where he knows everything etc. If that's the case and that's what the author is going for, they shouldn't have such a past life at all, it's much better to find any random reason for them having such insane amounts of knowledge and let them act like the teens they are, but with a huge knowledge bank. Just call it "inheriting the knowledge of a random super cultivator from the stars" or whetever, would make more sense than that they're millions of years old yet act like a child.