Sora, after abusing the Power of Waking, found himself in a strange new reality, one where beings of darkness besides the Heartless existed in the form of devils. But when the Heartless somehow appear in this world, he will have to use his keyblade in order to defend it.

Exiled into a new universe, Sora can only do what he does best, and that is to help others as much as he can while protecting the world from the darkness. That is, until he learns the reason why he was here. His friends may be out of his reach, but that doesn't mean he could make new ones... with some of them being his wives in the future. Edit: Not dead, just busy with school.

After the Final Battle with Xehanort the Keyblade Wielders split up to find Sora and protect the other Worlds from the Heartless. On her first Mission Xion safes a boy from getting murderd by a Fallen Angel but she herself dies. But she gets a second Chance as the Devil Servent of Rias Gremorey. A big Advanture awaits the former Replica in wich she finds new friends and foes.

honestly came to me when listening to 13th struggle while reading basically its a sacred gear based on the organization 13

This is a challenge of Kingdom hearts and highschool dxd involving Sora

There are other key blade users that travel worlds. Here is the story of one forgotten to time.

She was a Replica, a mere puppet destined to be forgotten upon her demise, but through the whim of a higher being, she was granted a second chance to live a life that she never had. How will she live this second life granted to her? No one can really tell. CHAPTER 02: A REPLICA WHO BECOMES A DEVIL

Meet Ken Asuragi - second year student of Kuou Academy. An individual who doesn't really stand out all that much and more of an observer than someone who acts. But, his life ends and just as quickly, it begins again.