I dont own Fairy Tail and Highschool Dxd.
After the Tartaros Arc. Igneel died and and Natsu promise that he will become strong as he leave Fairy tail to train in one year.What if Natsu suck into dimensional gap as he met Great Red and he train in 100 years which is equivalent a month in earthland. Great Red sent him to Highschool Dxd World and can go back after 1 year as he met his real blood sister and find new enemies and friend.
Will he survive in his new world? Full of technologies, buildings vehicles, Does it also said that there will be Angels? Fallen Angels? Devils?