A Fairy's Sword Game (Fairy Tail crossover with SAO)

*There might be spoilers in this fanfic about the newest Fairy Tail manga chapters.
*Natsu is 22 and Lucy is 21, Kirito is 21 and Asuna is 22
This will take place a year after the Avatar Arc when Lucy has gained new abilities and Fairy Tail is back together.
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It is now the year X794 Lucy has gone somewhere in Bosco to train herself for 6 months. Over those six months, she has gained the Star Dress Celestial Spirit Magic Spell, the key of Time and Space and a few other keys. After those 6 months she comes back the Fairy Tail in Fiore and shows the guild her new abilities and her new keys she has found and received. When she showed Natsu the Key of Time and Space they both were teleported to a different time period and world.

Kirito(Kazuto) and Asuna, have been going out and are now happily engaged. They now live in the same apartment in Tokyo, Japan and it is now the year of 2029. When they hear a knock on their, door, they see two people, a man and a women. Thinking that they are some drunk couple which happened to be cosplaying, they let them in hoping to get some information about them and on where they live.

Soon after they arrive, Asuna was then hit with some strange sickness which was then traced back to where Natsu and Lucy come from, Fiore. The only way to save Asuna is to now go back but the only problem is that there is insufficient amount of magic their world. How will they get back to Earthland and will they be able to save Asuna from this strange sickness?