Indra and Asura are also characters that are frequently paired with Hagoromo in fanfiction. These pairings often explore the family dynamics more closely, such as Hagoromo teaching them new skills or them helping Hagoromo in some way that was not shown in the original series.
One interesting concept could be exploring Hagoromo's early life in more detail. Maybe his relationship with his family members, like his mother or father, who are not much explored in the original series.
Saitama from One Punch Man would be an interesting pair. Saitama's simple yet overpowered nature could create an interesting dynamic with Hagoromo's complex and ancient powers.
One idea could be to cross Hagoromo Otsutsuki with a character from a different anime universe, like Goku from Dragon Ball. They could have a power - level comparison and then team up against a common enemy. Another plot could involve Hagoromo in a modern - day world crossover, where he has to adapt to new technology while still using his ancient powers.
In the fanfiction, Kaguya could start as a somewhat menacing figure but as she spends time with Hagoromo and Hamura, she begins to show her more vulnerable side. Hagoromo may develop his leadership skills as he tries to bridge the gap between Kaguya and Hamura. Hamura could develop his diplomatic skills as he has to deal with the complex relationship between the other two. Their character development would be shaped by the various conflicts and reconciliations they experience together.
One possible plot could be that Kaguya, before her fall into darkness, tries to teach Hagoromo and Hamura some of her unique jutsu. This could lead to a stronger bond between them and change the course of the events that later led to her downfall.
One way is to make the Otsutsuki OC a hidden observer during the Uchiha massacre. They could be there to study the Sharingan or the power dynamics within the Uchiha clan. For example, they might be interested in how the Uchiha's emotions, like hatred, are related to the power of their eyes. Another way is to have the OC be a factor that somehow influences Itachi's decision. Maybe they offer him a different option or some knowledge that makes him rethink his actions, but in the end, the massacre still occurs due to the complex web of political and clan - related reasons in the Naruto universe.
The Otsutsuki OC might be an unexpected bystander during the Uchiha Massacre. For example, they could have been on a different mission in Konoha when the massacre started. They might then decide to get involved, either to save some Uchihas out of a sense of justice or because they see potential in the Uchiha bloodline for their own purposes. So, they end up interfering with Itachi's plan and creating a whole new set of consequences for the story.
The Otsutsuki OC could be a catalyst. They might have some knowledge about the future or some power that the Uchiha want. This could lead to internal strife within the Uchiha clan as some members might be tempted to side with the OC for power, while others oppose it, which could be a contributing factor to the massacre.
Well, the OC might try to prevent the Uchiha Massacre. Maybe they have a different view of the Uchiha compared to the Konoha leadership. They could try to convince the Uchiha to flee or negotiate with Konoha. If they have unique powers or knowledge, they could use it to expose the real motives behind the planned massacre and create a situation where the Uchiha are spared. This would completely rewrite the story of the Uchiha's downfall.