Another interesting concept could be that the moon is a sentient being and an angel is its guardian. They have a special bond and together they watch over the Earth, and when the moon is in danger, the angel has to fight to save it.
One idea could be a story where a group of adventurers has to complete a quest during the blood moon. They face strange and powerful creatures that only emerge during this time. The blood moon's red glow could have some sort of magical effect on their abilities, either enhancing or hindering them.
You could write a fanfic where the main character is a Pokemon ranger in the Alola region. They are tasked with protecting a special area that is home to a group of endangered Pokemon. Along the way, they meet various trainers and have to deal with poachers trying to capture these precious Pokemon.
You could write a fanfic about a group of friends who all start their Pokemon journey in Alola at the same time. Each of them has a different goal and Pokemon type preference. As they progress through their journey, they face various challenges together and sometimes separately. Their relationships are tested and strengthened as they deal with difficult situations like facing off against powerful wild Pokemon or rival trainers.
A great concept for a Sailor Moon OC fanfic is an OC that has a special connection to the moon but not in the same way as Sailor Moon. This OC could have been created by an ancient civilization on the moon to be a protector. She might have different abilities like being able to control lunar phases for various effects, such as using a new moon to create a shield or a full moon to enhance her strength. Or an OC who is an artist, and she uses her art to fight the evil. Every time she draws something, it comes to life to battle the bad guys.
Another interesting concept is a love triangle. Suppose Ranma falls for Sailor Moon, but Tuxedo Mask is already in the picture. This could lead to a lot of comical and tense situations. Ranma might try to outdo Tuxedo Mask in protecting Sailor Moon, leading to some friendly rivalry. Also, his curse could add an extra layer of complication. What if he turns into a girl when he's around Sailor Moon at an inconvenient time?
One idea could be a story where Celestia tries to redeem Nightmare Moon. Maybe she delves into the past to understand what led her sister to turn into Nightmare Moon in the first place and uses that knowledge to slowly break through the darkness. Another plot could be a time - travel fanfic where a character goes back to prevent Nightmare Moon's creation, and has to work with Celestia to do so. Or perhaps a fanfic where Celestia and Nightmare Moon are forced to team up against a greater evil that threatens Equestria.
One idea could be exploring a different perspective of Jacob's transformation. Maybe focus on his internal struggle in a more in - depth way than in the original. For example, how he really feels about his new identity and its impact on his relationship with Bella from his own point of view.
First, you could start with creating the world. Decide what the relationship between the angel and the moon is. For example, is the moon a sacred object for the angel?
One idea could be a forbidden love story. A character from a light - loving clan falls in love with someone from a clan associated with the blood moon. Their relationship has to be kept secret as their clans are at odds.
One plot idea could be that Akeno and Issei have to go on a secret mission together. During this mission, they face various challenges that test their relationship and their individual strengths. This could lead to some romantic moments as they rely on each other for survival.