The Schoolgirl Secret Agent - Chapter 2773

After 10,000 years, it was iced. The Douro’s federal expedition team discovered an egg with a gold and silver two-color pattern during the scientific study in the northern part of the country. After exploring it with an instrument, it found that there were vital signs inside, and he quickly brought it back to the institute for incubation. The egg hatched, but it was a baby, a baby identical to humans, and an egg-born child.

- Description from ptwxz

The world was once at war with 10 alternate worlds. This was known as the Concept War and our world won 60 years ago. All of this was concealed so no normal people are aware of this fact in the current time.

After the death of his grandfather, the high-school student Sayama Mikoto is suddenly summoned by the giant corporation IAI. He learns this world is headed for destruction due to the acceleration of the Minus Concepts. To prevent this, negotiations must be undertaken with the survivors of the other parallel worlds so their 10 concepts can be released.

And so Sayama is caught up in the final battle to clean up after the Concept War which left behind so much enmity.

She never dreamed that she would meet him in the bathroom and they...Five years ago, she betrayed him for some reason and chose someone else, which deeply hurt him and he swore to make her pay the price. After the reunion, he launched a fierce attack on her, while she tried to escape this emotional entanglement.However, the red line of fate seems to have already tightly connected the two. Through repeated interactions and confrontations, they gradually uncovered their past misunderstandings and got to know each other again. His deep affection for her remained, and she was gradually moved by his sincerity.