Toaru Majutsu no Index - Volume 6, Chapter 1: Opening Ceremony. Baby_Queen.

A river song, triggered a legend of the rivers and lakes.
Tian Zun’s life motto: “My sword is the truth.”
Shen Lang’s life motto: “To serve people with morality, those who are dissatisfied are dead.”

- Description from uukanshu (translated)

I...AM...MOB CHARACTER!!!Sigh~My name is Samael, I was an office sla- I mean a worker who worked 9 to 5. It was a daily routine of monotony until one fateful day when I went home only to find my best friend with my girlfriend. Betrayal was the first thing I felt, followed by rage.And after taking ‘care’ of them, My surroundings changed…Looking at my reflection in a mirror, I noticed my appearance had changed. Gone was the face of the disgruntled office worker; instead, “SAMAEL ASHWOOD!!!” a character from a novel I used to read. But this wasn't just any character; I had become him—the sacrificial best friend of the protagonist who was betrayed and died in just the first two chapters.PROTAGONIST DIED!?[Heavenly Destiny System Initializing...][...]

Inexplicably reborn in the year 2003, having failed terribly in his previous life, the prevailing concern with Xu Tingsheng, that stands above all else, is none other than her. But alas, he is just months away from entering university, while she is but in her first year of junior high… Regarding this, all he can do is wait silently…for now.

After a series of life-changing events, Pei Ge decides to start anew and rediscover her place in this world. She gets a new job, new friends and… a new boss whom she mistakes as a male host!

He helps her to get revenge on a back-stabbing friend, supports her when it seems that the world has given up on her, encourages her to be more confident about herself and even… messes up her blind dates!

With her strong working abilities and fiery attitude, she manages to climb up the ranks in the company (under the devious scheme of a certain CEO) and even gains a fan girl who can’t wait to be her sister-in-law.

As Pei Ge navigates through the ups and downs of office politics, family drama, finding her right partner and societal expectations, she realizes that things are not as simple as it seemed and everything she had believed in is tested…

The Big Misunderstanding:

“You asshole! Why didn’t you use protection?! I’m pregnant!”
“…It’s not mine.”
“Asshole! You actually dare to not admit it?! I gave all my firsts to you! You jerk!”
…
At the gynecologist, she read her pregnancy lab report and was stunned: Irregular period.
The man raised an eyebrow and smirked, “Didn’t you make a ruckus about being pregnant with my child? Where is the child?!”
“…” Who is scared of who? Let’s make a bet!