Two reincarnated people from different times with only one mission, kill the hero.

One a girl who was a mage soldier for the Empire who was feared as Devil of the Rhine and Rusted silver (silver that rusted in the blood of her enemies) before she was killed in battle against the Russy Federation.

Another was a boy who was once the world's most deadly assassin known to all simply as Ghost, he was feared for always getting the job done before he was killed by his pupil.

This brother and sister duo must now grow in power houses that are capable of fighting and kill the hero within the two year span after the demon lord's death.

Will the two be able to make it and make the kill, or will they die in vain like their previous lives.

The main characters: Tanya → Asselina
Allen → Desmond

This book was inspired by Two Worlds’ Finest written by SwissChocolates. I've only read/watched Youjo Senki/The Saga Of Tanya The Evil and never got into The World's Finest Assassin Gets Reincarnated in Another World as an Aristocrat so my ideas on whatever happens in that series is vague at best.