The story could develop with Issei forming his own group. He might gather other characters who also feel left out or have similar goals. This new group could then become a rival to Rias' peerage, leading to interesting battles and power plays.
One possible reason could be a desire for self - discovery. Issei might feel that being in Rias' peerage limits his growth in certain ways. He may want to explore his powers and identity on his own terms.
One idea could be that Issei leaves Rias because he realizes he has different goals in the supernatural world. He might want to focus on helping the weaker devils rather than being part of Rias's peerage. So he sets out on his own journey, making new allies and facing new challenges.
The dynamic within Rias' peerage would be greatly affected. There would be a power vacuum as Naruto is likely a strong member. His departure might cause some members to question Rias' leadership. Maybe they start to worry that if she couldn't keep Naruto, who else might leave? Also, in battles, they would have to find new strategies without Naruto's unique abilities.
The pregnancy in the fanfiction could also bring about a new era for their group. It could be a symbol of hope and new beginnings. Issei and Rias' relationship could become an example for other characters. The story could explore how they prepare for the baby, like setting up a nursery in their supernatural abode. There might be a time when Rias' powers are affected by the pregnancy, and Issei has to step up even more to protect her. And as the due date approaches, the excitement and nervousness among the entire group would be palpable.
In a Naruto - Rias' peerage fanfiction, the story might focus on how Naruto's chakra system interacts with the devil's power. For example, his ability to sense chakra could be enhanced or changed when combined with devilish senses. Also, his relationship with the members of the peerage would be interesting. He could form strong bonds with some, like Kiba in Naruto's world, he might get along well with the werewolf in Rias' peerage.
Naruto in Rias' peerage would be quite a sight. His orange jumpsuit would stand out among the devils. He might use his shadow clones to do multiple tasks within the peerage, like scouting or helping with household chores. His positive attitude would also have an impact on the often - serious devils in the peerage.
Well, one possibility is that Naruto's unique skills and his never - give - up attitude would make him a great asset to Rias' peerage. His shadow clone jutsu could be used in various strategic ways during battles. For example, he could send clones to scout the area while the main group plans their attack. His rasengan could also be a powerful offensive move against their enemies. And his ability to make friends easily might also help in building stronger bonds within the peerage.
If Issei leaves Rias, the power dynamics in the story would shift drastically. Rias's peerage would be weakened without Issei's strength. Also, Issei would have to find his own place in the devil world. He might explore other areas of the supernatural and form new relationships.
A fanfiction about Issei marrying Rias could explore the cultural differences within their world. Since Issei is human - turned - supernatural, and Rias is from a noble devil family. Their marriage could be a blend of human and devil traditions. They might incorporate elements like a human - style wedding reception with food and music, along with devilish ceremonies that are unique to Rias' family heritage. This would make their marriage a truly special and one - of - a - kind event in the fanfiction world.
Yes, there might be such fanfictions out there. You can try searching on popular fanfiction websites like Fanfiction.net or Archive of Our Own. Just type in the relevant keywords and see what pops up.