AN important: This is going to be 18+ fanfic idea.

Changes in Naruto from canon: The age of passing academy is 15 to join Genin team. This is the only change. I hate shota x oneesan shit.

Changes in DxD: Rias actually needs to remain maiden for the marriage contract. Otherwise, it will become null. Same goes for Riser who just controls himself enough for not having sex with his peerage, but he still abuses them.

AN2: can be done as a one-shot fic or much more.

Idea:

Naruto is escaping Mizuki after he tried killing him to steal forbidden scroll of seals. Naruto in his infamous orange jumpsuit is easily spotted by Mizuki, and mizuki throws his Fūma Shuriken towards Naruto who is too scared to move from incoming threat. (Here no Iruka)

Just as the Fūma Shuriken was about to hit Naruto a magic seal appears below him which teleports him.

(An hour ago, before Mizuki throws his Fūma Shuriken)

Gremory Household

Rias is captured by his father and imprisoned in a cell (her room) because she refused to marry Riser. This happens just after she tried to have sex with Issei.

Rias was devasted by this development. She tried to break free from her prison (her room) but none of the spell worked due to the magic sealing seals placed on her. She was so desperate that she tried everything, from physical force to her magic, but those damn seals didn't allow her.

Then she remembers that she "accidently" read a dark magic summon book which didn't required any magic to activate, but required the summoners blood for the ritual. She looks around, but finds no knife or any sharp objects. In desperation she breaks a flower pot and uses the sharp edges to cut her hand to draw blood. She starts drawing the ominous looking magic circle using her blood.

After finishing the circle, she chants the incomplete spell which she glanced through, hoping that it may work. Surely nothing will go wrong, she thought.

(Now back to Naruto)

Rias's summon was successful, she was hoping for a vicious monster who will cause chaos giving her a chance to escape. But on contrary, a frightened boy appeared in front of her. The magic seals on her body were released giving her control of her magic once again. Forgetting about her immediate problem (Naruto) she tries her teleportation spell, but nothing happens. Surprised, she tries destruction on the door of her room, but the gate doesn't disintegrate (you can write her agony).

Then she turns to her summon. Now the only chance for her survival (not marrying Riser) is in front of her. Desperate she binds Naruto with her spell and says a sorry to his ear before proceeding to do the deed. ( ͡° ͜ʖ ͡°)

Finishing with her deed she casts a spell on Naruto so that he will forget all things which happened to him, but she forgets that there is another soul inside Naruto who was watching the whole thing with a smug on his face. Kurama just saw something that can be used against Minato, who divided him into two halves.

Cancelling her spell she returns the summoned boy to his original world, and proceeded to wait for her father to release her on the day of her marriage.

Naruto was rescued by Anbu searching for him throughout the forest. Surprisingly he was missing for a full day.

(Fast forward when Naruto was about to remove kurama's cage seal during pain arc)

Kurama didn't had to wait long as the opportunity for his revenge presented itself. He was about to tell Naruto about his "one missing day", he was stopped by Minato who made a deal with Kurama that he will give his other half if he doesn't tell Naruto about his "missing day". Kurama grins and accepts his offer.

Minato tells Naruto about his dead body and where it is kept, so that he can use that body to let kurama have his other half, to keep his side of the deal. He also tells him that the seals will be strengthen accordingly.

Before Naruto could get Minato's body, it was already taken away by Orochimaru to be used in edo tensei. Kurama is devastated, he didn't tell Naruto about the "missing day" because he didn't have any grudge against him. His enemy were Madara and Minato.

(Fast forward to Kaguya vs team 7)

Kaguya goes berserk as both sun and moon seals touches her. She starts using her Rinne-sharingan to open dimensions after dimensions. Sasuke using his quick thinking reaches out for his teammates and sensei, and uses his rinnegan to return them to their original dimension. But just as they were about to escape from the gate opened from sasuke's rinnegan, black jetsu stretches his body and latches onto Naruto and Kaguya uses her last ounce of chakra to transport Naruto into another dimension (HS DxD dimension).

(Naruto get's transported to DxD universe but only 5 days have passed there. Rias will have difficulty recognizing him when they will first meet.

Request:

Please don't make Naruto part of any peerage, or devil at all.

This can be a great gag and romance fanfic.