Naruto might also use his blood control to enhance his physical abilities. For example, he could increase the oxygen - carrying capacity of his blood to boost his stamina. Or he could control the blood flow to his muscles to increase their strength momentarily. This would make him an even more formidable opponent in combat, and these applications would make for some really interesting scenarios in the fanfic.
His blood control ability might also create new alliances or enemies. Allies could see his power as a great asset and join him, while enemies might fear his newfound ability and target him more aggressively. In the context of the fanfic, this would add more twists and turns to the plot. Maybe some characters who were neutral before would now side with Naruto because of his blood control, or some of his old enemies would form stronger alliances against him.
Another feature is the character development centered around the blood control ability. Characters may struggle with the morality of using such a powerful and somewhat gory ability. They might have to overcome their own fears or the prejudice of others. In some fanfictions, characters with blood control abilities are ostracized at first because it's seen as something unnatural. So, it makes for really interesting internal and external conflicts.
Maybe he can control the metal in the earth to create underground tunnels or barriers. It would be a great way to surprise his enemies or protect his allies. He could also use his power to manipulate the metal in machinery, like disabling enemy weapons or enhancing his own tools.
One unique application could be that he uses it to relive his training days and improve his skills even more. He can go back to his time with Jiraiya and learn from his mistakes during training. Another is that he can slow down time during a battle to dodge attacks that are otherwise too fast for him.
A possible drawback is that it might require a great deal of concentration. Naruto is already dealing with a lot in combat, like using his various jutsu and strategizing. Adding blood control to the mix might overtax his mental resources, making him vulnerable to attacks. Also, if his enemies figure out his new ability, they could try to counter it by using techniques that disrupt blood - related manipulation, like creating strong chakra fields around their bodies to prevent him from accessing their blood.
Well, it could be related to some kind of forbidden jutsu he discovers. Imagine Naruto finds an ancient scroll that details a jutsu which allows the user to control blood. He spends time mastering it, and once he does, he can use it to sense the presence of enemies by their blood flow, or even restrict their movements by solidifying their blood inside their veins.
Well, you could create a character who has the ability to manipulate their own blood like a weapon. For example, they can turn their blood into sharp projectiles or use it to form a protective shield. This would be a really unique power based on blood.
Well, in some fanfictions, 'naruto blood needles' might be a unique jutsu created by the author. It could have special properties like being able to pierce through powerful defenses or having some sort of tracking ability. Maybe it's a technique Naruto develops after a really intense training session or a life - threatening encounter.
One interesting 'Naruto Blood Fanfic' could be about a hidden bloodline ability that emerges in a minor character. For example, a character discovers they have a bloodline that allows them to control the shadows in a unique way, different from Shikamaru's. This could lead to a whole new set of adventures and challenges as they try to master this power and fit into the ninja world.
Physically, he might gain new powers or abilities as mentioned before. But there could also be negative effects. His body could reject the foreign blood, leading to internal pain and weakness.