Rakuin no Monshou - Volume 11, Chapter 1: Rumblings

After breaking up with his girlfriend, he accidentally acquired a genius system and rose from there against the heavens, becoming invincible..

- Description from Novelupdates

One day every human on the world suddenly receives a mail claiming to enact the World Salvation Project. Half in doubt Kurosaki Shion, a diligent university student and loner, follows the mail’s instructions, becoming one of a million Demon Kings governing his very own Domain in the new world.

*** This is a post-apocalyptic story containing many fantasy elements. It is a somewhat dark tale following Shion as he grows while aiming for the unification of the all too sudden new world. It has many game-elements bolstered by strategical thinking while at the same time providing funny moments and romantic encounters.

The young lady from the Xue family was talented and beautiful, and married the dream husband at the age of 16. They had a loving and harmonious relationship and were together for 3 years when her husband attained the title of Imperial Scholar.

“From today onwards, you will become the Envoy of one of the Main Gods in the Dimensions of Gods. You will travel from one world to another and through that, you will attain what others will never obtain in their entire life.”