Astolfo x Konatsian Male Reader

(Y/N) was a normal high school student, he was decently well known in his grade, excelled in his classes and overall lived a normal life like most. But secretly, he is from the race of the Konatsian's and is the vessel of the benevolent phantom majin Hirudegarn. Eventually he meets the new transfer student Astolfo and the 2 quickly grow close to one another, with this new development came beings of evil that went after the 2 for one reason or another, with Hirudegarn slowly trying to break free from (Y/N) and the forces of evil against him and Astolfo. Will (Y/N) and Astolfo overcome the evil and find a way to contain and control Hirudegarn? (I do not own any characters from Fate/Grand Order and Dragon Ball)