Zero no Tsukaima - Volume 15 Chapter 8

This is a world shrouded in darkness, and the pervasive black mist erodes all living beings.

Only fire can dispel the darkness and protect mankind.

But the firewood will eventually run out, the fire will eventually go out, and humanity will eventually perish.

until Rhodes came.

- Description from novelbuddy

As a precocious child, Lycoris suffers from a strange sense of deja vu. On the day her father told her about her fiancé, she realizes that her fiancé was a character from an otome game she once played in a previous life.

Ali Avery was a successful young man adored by everyone. But things were not as they were shown to the life. Shunned and betrayed by his peers... He was hiding among happy facades.

In the endless Universe is eight primordial laws. Each of the eight laws have been fused with a supreme expert, but unbeknownst to everyone, there is a ninth law in the universe. It tears open the Primordial Chaos and is beyond reach.

Di Jiu—whose name is a homophone for ‘ninth’—is the ungifted son of a powerful Di family clan in the Ji Nation as he lacks martial roots. Unwilling to resign to his fate, he practices medicine, hoping to one day cure himself.

- Description from Novelupdates