I Become Karna With a Million Times Crit System In Mahabharata. - Chapter 118 117. It’s For Peace

Dying in a tragic accident Marcus Ferrous gets transferred to a fantasy world of monsters and magic, except when he arrives contrary to what he expected he is now level one and a ghost. Left with nothing on a strange new world, Marcus will struggle with everything he has on his journey to get stronger and uncover the secrets of his new world.

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.

Childhood sweethearts.
The most popular person in school is my childhood sweetheart.

- Description from Novelupdates

In the shadow of Silver Peak Mountain, the Winter Moon Festival approaches - a party where wolves find their true mates. For 18-year-old Lily Carter, being an omega means living on the edges of pack life, watching others find love while she expects to be paired with another forgotten omega. All her life, she's watched Luna, the Beta's daughter, receive admiration from everyone - especially from the Alpha's triplet boys who will one day lead the pack.But on the night of Lily's 18th birthday, which falls during the festival, her world shatters when her fated mate mark shows - linking her to one of the three powerful brothers. Now Lily must manage jealousy, dangerous pack politics, and her own insecurities as she tries to discover which brother is truly meant for her. As threats emerge from within and outside the pack, Lily discovers hidden strengths that show she's far more than “just an omega.” With three potential mates - the charming diplomat, the fierce warrior, and the thoughtful scholar - Lily's destiny is far greater than anyone could have dreamed.