One common theme is love and romance. Since it's about Rias Gremory and a male reader, there's often a development of a romantic relationship between them.
Yes, there are many. You can check some popular fanfiction websites like Archive of Our Own. Just search for 'rias gremory x male reader adventure' and you'll likely find some great reads.
One common theme is the development of a romantic relationship. The story often shows how the male reader character and Rias gradually fall in love. Another theme could be adventure, where they go on quests together.
One common theme is protection. Rias, being possessive, often tries to protect the male reader from various threats, whether it be other characters or dangerous situations. Another theme is jealousy. Her possessiveness leads to jealousy when other characters get too close to the male reader.
The 'rias gremory light novel' has themes of friendship. Rias forms strong bonds with her comrades. Additionally, there is the theme of redemption in some cases. Some characters are given the chance to atone for their past mistakes. And of course, the theme of good vs. evil is present, though the lines between the two are often blurred in this complex supernatural setting.
A common theme is self - discovery. The male oc often has to figure out his place in the Gremory world and what his powers or abilities truly mean. Another theme is friendship. He usually forms strong bonds with members of the Gremory family or other characters in that realm.
One idea could be that the OC is a new transfer student to the school where Rias Gremory is. They accidentally discover a hidden power within themselves that Rias is interested in. So she takes the OC under her wing, and as they train together, a deep bond forms between them.
Maybe there is an ancient prophecy in both worlds that foretells of a union between a wizard and a demon. Harry Potter and Rias Gremory are unknowingly the ones mentioned in the prophecy. As they are brought together, they first resist the idea as it goes against their own beliefs. However, as they face various threats, like a group of rogue wizards and demons who want to stop the prophecy from being fulfilled, they start to see the value in each other. They combine their unique magical abilities and ultimately fulfill the prophecy, bringing peace and a new era of cooperation between the two worlds.
One common theme is the exploration of different magical systems. Since Harry Potter has its own set of magic and Veneela Gremory comes from a different magical context, fanfictions often focus on how these two magics interact.
One potential plotline could be Naruto being summoned to the world of Rias by accident. He then has to figure out how to get back home while also getting involved in the power struggles within the devil world. Maybe he becomes a key player in a battle for control of a certain territory.
Love against all odds is a typical theme. In many male x male reader fanfiction, there are obstacles like family disapproval or social norms that the characters need to overcome to be together. Friendship is also often intertwined, as the relationship may start as a friendship and then develop into something more romantic.