I'm just gonna say this now this idea is based on another story that i sadly can no longer find on this site but i'm gonna add some things to make it different from the original or at least what i can remember from the original so here's the idea.
Naruto Uzumaki Former Exorcist Extraordinaire is currently trying live a peaceful life in early retirement but that peaceful life comes to an end when he meets a young red haired boy that is not only the son of the devil but his old flame as well "Why does this shit happen to me."
If that doesn't jog your memory i'll just say it Grayfia after a fight with Sirzechs had a brief affair with Naruto but left after Sirzechs found out and took her back to the underworld despite Grayfia having not done anything serious with him she genuinely developed feelings for Naruto and regrets leaving him. Meanwhile Millicas tired of seeing his parents fight decides to run away from home not unsurprisingly he runs into trouble but is saved by Naruto and decides to stay with him not knowing he's the reason why his parents are fighting in the first place. And finally Sirzechs just wants to keep his family together but is torn between his duties as Maou and his duties to his family making his attempts slowly but surely make things worse.
so yeah that the idea again i can't find that story anywhere so i'm just doing this from what i remember but again i'm gonna add some changes that (i think?) weren't in the original like.
The church trying to get Naruto back.
Rias unknowingly help pushed Grayfia into choosing Naruto.
and various supernatural figures getting involved now that they think that Grayfia is single.
I say one last time i am not writing this this is a challenge for someone else and if you take this challenge you can add whatever you to it like.
A Harem if you so choose all i ask is that Grayfia is the main girl
and last but not least lemons since the original ended before it got that far. (Seriously the last chapter i remember imply's that Grayfia choose to be with Naruto and that was it)
Thank you for your time and if you choose to take this challenge please don't hesitate to contract me cause again i'm doing this challenge from memory and i like to think that i have good memory but you want to do your thing with it i understand.
For all i know your probably not even gonna read this but if you did read this far than once again thank you for your time and have a good day or night where ever you are.