Demon Slayer x Fairy Tail

Another Explanation

This is how my fanfic world and timeline works

Lucy was 16 when she 'ran' away.

Explanation of what happens during the 5 years

During the Ten year mission Lucy goes back to being the Elemental
Hashira after 8 years of break (Years X784 - X791) since there were previously no demons in Fiore until Tartaros. Rengokou is sent to help his girlfriend out in the 1st 6 months of the 1st year of the mission with demons from Japan as there had been some sightings of the Upper Moons

Before the start of the 5-6 year mission, Tanjiro's family is still alive during this time until they die, during the 7 months before the 1st year of the mission he begins his training for a year, he travels around for 6 months fighting/slaying demons. In the 2 year, Tanjiro, Inosuke, Zenitsu, and Nezuko goes to Fiore to help Rengokou.

Tanjiro and the Gang finds Rengokou and Lucy + Happy, they train together for a year. Everything after that will be explained in the story.

Lucy and Rengokou are immortal, in the way that if they die they come back to life in 1 year or less depending on how much damage was done to their body. So when Rengokou fought Akaza and 'died' his body took 2 months to regenerate again in the realm/world the two created, hence why people though he actually died because they couldn't find the body. How this takes place will be explained in later chapters

Rengokou calls Lucy, Liezel and Lucy calls Rengokou, Ren.