Naruto: Kuroryuukou
This is an idea i had for some time, since my first idea wasn't accepted, I hope someone get interested in this one and sends me a message to my PM.
Naruto is born in the DxD universe as a high class devil, he is the older twin of Sona Sitri, and a childhood friend of Rias Gremory, you can change the title.
His peerage he will meet each member individually and it consists of:
King: Naruto Sitri
Queen: Valerie Tepes
Bishops: Kuroka, Elaine Westcott (She is the lover of Arthur and the one who teached magic to Le Fay)
Knights: Arthur Pendragon, Jeanne
Rooks: Bikou, Fenrir
Pawns: Vali Lucifer (2 mutated pawns), Le Fay Pendragon (3 Pawns), Xenovia (3 Pawns)
Naruto will create an artificial sacreg gear with the help of Azazel, by using the Sephiroth Graal to study Vali's Divine Dividing, then they will seal the soul of Apophis the Evil Dragon inside the sacred gear. The abilities of the sacred gear are the same as Apophis:
Umbrakinesis
Dark Field Barrier
Primordial Water (This power Naruto will remain locked until Naruto unlocks it like Vali unlocked Reflect, and Issei unlocked Penetrate)
Balance Breaker (An black armor with silver jewels like Apophis)
Juggernaut Drive
Naruto has to be stronger than Vali, but not too much, and also he can't fight on par with Satans or Gods.
Everyone in Naruto's peerage doesn't have weakness to light or dragon slaying attacks, because Valerie's Sephiroth Graal removes their weaknesses.
Naruto's Harem: Rias, Valerie, Kuroka, Xenovia, Jeannie, Le Fay. (others can be added except Grayfia, Yasaka, Serafall or Ophis).