.....Finally we see that the other world and the world in the manga are actually connected and that what happened in that other world affects the prime world as well.
@ekickx
He spent years in the other world and only hours passed on earth, so its entirely possible for her to have grown up and found a way to transfer to Earth.
@Capt_Gigglepants
Or she could have died and reincarnated into his world at an earlier point in time than when he was transfered to another world or grew up after transferring to his world. All we know time and space could be f***ed up between the two worlds like in that one manga with the protagonist named Rio who had the childhood friend dissappear before he died in his original world. Also there could be a possibility that he didn't actually get sent to another world and in his world magic existed and the past and is practically forgotten now except for a few people and history was basically overwritten and the angel girl has an extremely long life span and took the long way through time while he took the short way (again a plot from another manga I forgot the name of just that the MC didn't return to his own timeline)
huh? was she reincarnated along the time axis of earth after she died in her original world. he was transported back to the exact moment he was summoned. so it aint time dilation.