Well, I'm going to need your help again because I'm about to start Chapter 2 of this fanfiction, and I've come up with one solution. And I'd like to hear your thoughts before I start Chapter 2. Also, if you have any better suggestions or ideas, please send them to me via PM or write them in the reviews.

Option: 1. As you know, in my Greek version, Naruto is depressed but uses his depression as motivation to work out, whereas in the DxD version, Naruto is depressed for a while (4-6 months) and then is attacked by a stray devil or fallen angel on his way home from work or something. Naruto made the decision to ignore the supernatural after learning about it for so long, but after this one attack, Kurama sees it as an opportunity for Naruto to move on with his life. After realizing that magic and chakra are somewhat similar, Naruto will then enter the underworld. Naruto will draw a lot of attention, both good and bad, after entering the underworld, but he will turn everyone down until four young, brave devils approach him and ask to be trained by him. After recognizing some of their potential and traits that mirrored his own, they would accept Naruto's offer to train them. (Female Sirzechs and Serafall would fall in love with him here, but fear and the ongoing war would make them decide not to act on their feelings.) With Naruto on their side, they would gradually begin to win the civil war during a raid on a house. Naruto would meet Grayfia and, after seeing and speaking with her, would decide to let her go. Female Sirzechs would then be informed of what had happened between them, and after receiving a letter a few weeks later, she would tell them that she would like to meet them for a chat in an undisclosed location out of concern for his safety. While they were there, they would persuade Grayfia to betray her household. After a few more months of fighting, they would eventually win the civil war, feeling a sense of accomplishment in assisting them. After overcoming his depression and sadness, Naruto would decide that it would be best for him to leave and explore more of this world. He would then decide to leave the underworld, which would break the hearts of the female Sirzechs, Serafall, and Grayfia. All three women have fallen in love with Naruto due to either his kind and loving personality or his leadership, looking for the good in people, and his humor. (As for the Olga Discordia, Chole, they would be dark elves and lead their own race, but they would still be allied with the devils; similarly, Celestine Levantine and her light elves would be allies with the angels.)

Keep in mind that this isn't the whole story. Additionally, I've already planned out how each woman in Naruto's harem would fall in love with him.