MTL - Extreme Knight - Chapter 500 mixed rules

Vincent Strider was a gun for hire who made a living by killing whoever it was his clients wanted dead. But during one mission, he died in a fierce gunfight. However, death was not the end for him. Vincent found himself reincarnated in another world, facing a floating interface that flickered before his eyes.[Synchronizing Host!][Military System initializing.]Vincent found out that in this system he received, he can summon soldiers, tanks, aircrafts, and even warships! This is going to be exhilarating.

While trying to survive, Eddie needs to create his Serum. But, all these works make his life pressure continues to grow.Especially after he meets Ada Wong.All he can do is 'Fighting' with the female Wesker to calm the stress.As for Alex, Jill, and Rebecca. Eddie *cough* does not know them... Maybe just friends that like to hang out and drink coffee together?Wait... You tell me they all had children?In the future?Ah, I see... Still, who is the children's father?

Collection of short stories.

- Description from Novelupdates

The end of all worlds approaches.

The Demon King Order harvests lives from all manners of living beings.

Within this darkness full of despair,
A single person escaped from space-time, returned to before the world collapsed, determined to change the fate of the past.

But as time pass, he gradually finds out that the Apocalypse isn’t quite as simple as he thinks…

- Description from novelupdates