Welcome to Nivon is by -BtsArmyForever- and here is the description

When Jeon Jungkook travels through a protal and finds himself in a new, mysterious world, the first person he sees is a boy named Kim Taehyung, who promises him the he'll send him back to earth in no time. Will Taehyung succesfully send Jungkook back to where he belongs, or will he fail miserably? Will he be able to make Jungkook smile, or end up being hated by Jungkook for trapping him in a unkown world, far from home? What if feelings peek in?

I love this stoy so much it is so good it is Jammed packed with actiona and I love it. Good Job -BtsArmyForever- keep up the good work