Here is a less formal introduction:

I traveled through time and seemed to be an employee of a company.

Wow, that's a lot of salary!

The alarm sounded.

Asking me to suppress the minions? What the hell is this company?!

The following is a serious introduction:

I am Ye Lan. The best employee of Lobotomy Corporation in X0XX. Miss Hod doesn't even need to do core suppression after seeing me.

But no one in the company knew that I was actually a spy from a company in a world even outside the ruins. (Of course, Miss Angela might know this, but she didn't tell anyone, so no one knew.)

But besides this secret, I have another one.

A secret that even my real company doesn't know: I'm a time traveler. (But maybe I've told Miss Angela about this in one of my previous loops.)

Li You traveled to a wasteland world left behind by a magical civilization and turned into the immortal witch Yvette. After living for more than a thousand years, he finally decided to come out.

Then she discovered that she seemed to be the only survivor of this civilization.