First, you should brainstorm ideas about the mind bloodline. Decide what unique abilities it has. Then, create a main character who either has this bloodline or is affected by it. Next, think of a conflict. Maybe it's a battle against others who want to use the bloodline for evil.
To start writing a Naruto bloodline experiment fanfiction, you should start with a strong concept for the experiment itself. Maybe it's an experiment to bring back an extinct bloodline or to enhance an existing one to an extreme level. Then, focus on the character's motivation for participating in the experiment. Is it for power, revenge, or to protect someone? After that, create a conflict. It could be internal, like the character struggling with the new powers they've gained, or external, such as facing opposition from other ninjas who fear the power of the new bloodline. This will form the basis of your story and keep readers interested.
In some fanfics, Naruto absorbs the bloodline through a special jutsu. For example, he might find an ancient scroll that contains a jutsu allowing him to transfer and absorb the genetic traits related to a bloodline.
His relationship with the Hidden Leaf Village as a whole would change. The village might see him as even more of a savior or a potential threat, depending on how they view Asura's legacy. Some might fear that Naruto's connection to Asura could bring about a great change, either for the better or for the worse. Naruto would have to deal with these new expectations and attitudes from his fellow villagers while still being true to himself.
One way to blend the worlds is through the concept of power. Asura Wrath has incredibly powerful and god - like beings. In a fanfic, you could have Naruto characters encounter these powerful entities. For example, Naruto himself could meet Asura and learn about a different kind of chakra or power source. This would not only introduce a new element to the Naruto world but also create an interesting dynamic as Naruto's ideology of never giving up might be put to the test against the seemingly invincible Asura.
In this fanfiction, Naruto becoming Asura could bring about a whole new level of power. It might change his relationships with his friends and foes alike. For example, his connection with Sasuke could take on a different dynamic as he becomes a more god - like figure. His abilities would likely be enhanced to an extreme degree, allowing him to face threats that were previously insurmountable.
The knight bloodline could be integrated as a foreign power that was brought to the Naruto world long ago. Maybe a group of warriors from another dimension with the knight bloodline came and settled, and over time their bloodline got diluted but still resurfaces in certain individuals.
He might use some special jutsu or seals. For example, he could use a sealing technique to suppress the signs of his bloodline. This way, others wouldn't be able to detect it through normal means like sensing chakra.
It could also be part of a strategic move. By hiding his bloodline, he can surprise his opponents in battle. They would underestimate him based on not knowing about his true powers, and then he could turn the tables on them when the time is right. This gives him an edge in combat situations.
There are also fanfictions where a bloodline is created through some sort of experimental jutsu. For example, a bloodline that allows the user to transform into different elements at will. This would give the character an edge in combat as they could adapt to any situation by changing their form.