Reborn to be Royal R2BR

Summoned to another world after death, 21 year old Kai Warrens swore to the heavens that he would do whatever it took to survive in the next world. Now reborn into the body of 16 year old Kai Opius, Can he stay true to this conviction as he battles with onslaughts of dark forces? Or will the naïveté of his old, sickly self reveal itself once more in the face of those he will come to call family?