There might be his childhood friend who also gets into gaming. In the fanfiction, they could have a friendly rivalry that eventually turns into a great partnership. Their dynamic would be interesting to explore, as they know each other well from before the gaming days and now have this new shared passion.
The OC would first need to adapt to the Senju's strong sense of family and clan loyalty. They would have to learn the clan's traditions, like their unique way of training. Maybe they would start by observing the other Senju members and then gradually participate. They would also have to get used to the Senju's natural - based ninjutsu, which might be very different from what they knew in their past life.
First, study the Senju clan's traits in the Naruto series. They are known for their strong life force and connection to nature. So, give your OC Senju a power or ability that reflects this, like the ability to sense the health of living things around them. Second, think about their personality. Maybe they are kind - hearted because of their clan's values, but also have a stubborn streak. Third, give them a backstory that ties them to the Senju clan, like being the descendant of a famous Senju warrior.
Sure. There are some out there. The idea of Naruto being related to the Senju clan opens up a whole new realm of possibilities in the Naruto fanfiction world. For example, it could change his relationships with other characters. If he was Senju, his connection to Sasuke, who is an Uchiha, would have even more depth considering the historical rivalry and connection between the Senju and Uchiha. And it might also give Naruto access to different jutsus and abilities that are unique to the Senju.