Highschool DxD the son of skeleton dragon king

A teenager called Kai was raised in a church as an orphan. But he then moves back to Japan because of the old church being too small for the other children to live in so Kai returns with his new girlfriend Mia,but fate has plans for just having one lover and meeting an old friend from the past before he moved also the truth behind his origin before he ended up in the hands of sister Vivian and the farther of the church.