Maou-sama no Machizukuri! ~Saikyou no Danjon wa Kindai Toshi~ - Volume 1 Chapter 7

A college student was returning home after studying abroad for several years when the end of the world happened. A dragon appeared out of nowhere and attacked the plane he was in, thanks to an incredible amount of luck and his quick-thinking, he managed to survive the plane crash only to get stuck on a tropical island. A weird system took over the world and brought monsters to Earth. While nations collapsed and the world as a whole was being destroyed by ridiculous monsters, Leon was stuck on a godforsaken island with no chances of being rescued. What will happen to him? How will the world change while he is away? Will he even manage to return? The story, all names, characters, and incidents portrayed in this production are fictitious. No identification with actual persons (living or deceased), places, buildings, and products is intended or should be inferred.

The Immortal Path led to Longevity and Sovereign was heading in ease. When the Longevity was no longer in ease, all living beings were just prisoners. Conspiracy, internal strife, and the invasion of the others, all of it emerged together. 

In such a world, there was such a young man. He made his way upstream, stepping on blood, defying the emperor, destroying the various kings, and slaughtering his way through the hundred clans to form an Immortal Path towards the throne of Sovereign! The Immortal Path was endless, while the Sovereign was limited. He used his blood to forge his immortal legend.

- Description from Novelupdates

I was proposed to by the Final Boss.