The storylines could be blended by having a shared goal. Suppose there is a threat that endangers both the Naruto world and the Sekirei world. It could be a new, powerful and evil force. Characters from both series would then have to work together to defeat this threat. Along the way, they would learn about each other's worlds, powers, and cultures. For instance, Naruto characters could teach Sekirei about teamwork in the context of a ninja squad, while Sekirei could show Naruto characters their unique way of bonding with their Ashikabi.
Naruto's chakra could potentially enhance the Sekirei abilities. For instance, if a Sekirei has a power related to speed, Naruto could use his chakra to further boost that speed. His Rasengan could also be modified when combined with a Sekirei's power. Maybe it could take on new forms or have additional effects.
The storylines could blend by having Naruto enter the Disney princesses' worlds through some kind of magic portal. For example, he could end up in Aurora's forest and help protect her from Maleficent while also teaching her some self - defense ninja moves.
Well, one way is to have a portal that connects the two worlds. Characters from both sides accidentally pass through it. Then they have to figure out how to get back while dealing with the problems in the other world.
Well, in fanfiction, anything is possible. Maybe Naruto gets transported to the Sekirei world through some sort of magic or a strange portal. This could be the start of his journey to become a Sekirei. It could also be due to a curse or a wish gone wrong that transforms him into a Sekirei - like form.
Another approach could be to focus on the idea of leadership. Shepard in Mass Effect was a great leader, and Naruto also grows into a strong leader. A story could be crafted where they exchange leadership styles. Maybe Naruto teaches the Andromeda crew about the importance of unity and believing in oneself, while the crew from Andromeda shows Naruto more strategic and technological ways of leading. This could lead to some really unique character development in both universes.
Often, the storylines blend by having characters from Naruto end up in the Highschool DxD world. For example, Naruto might be summoned there by some sort of magic accident. Then, he has to navigate this new world full of devils, angels, and other supernatural beings while still having his ninja mindset and skills.
Well, in some fanfictions, Naruto and Hanabi might be transported to the Sekirei universe. Hanabi could learn new techniques from the Sekirei, while Naruto uses his Rasengan and Sage Mode to help in battles. There could be a love triangle involving Naruto, Hanabi and a Sekirei. Maybe Hanabi develops feelings for a Sekirei, and Naruto has to help her figure out her emotions while also dealing with the chaos of the Sekirei world.
The storylines can differ in many ways. In the original Naruto series, the focus is mainly on the ninja world, its politics, and the battle against evil forces like Akatsuki. In a crossover, new threats could emerge that are related to the Sekirei world. For example, a group that wants to use both ninja and Sekirei powers for their own malicious ends. Also, the relationships in a crossover can be different. Instead of just the typical Naruto friendships and rivalries, there could be romantic relationships between Naruto characters and Sekirei, which is not a part of the original Naruto plot.
Writers often start with a what - if scenario. What if Naruto was born in the Mass Effect universe? How would his life be different? They use this as a starting point to blend the storylines. They also consider the political aspects of both universes. The complex politics in Mass Effect like the council races and the ninja village politics in Naruto. By making characters interact with these political systems, they merge the two universes' storylines.
One way their worlds could blend is through a shared mission. For example, Naruto could be on a quest in a world that has been invaded by some kind of digital threat. Vocaloid characters, with their unique abilities related to music and data, could team up with Naruto to fight this threat. The Vocaloid's music might have special powers in Naruto's world, like being able to soothe angry demons or boost the strength of the ninja. Naruto's ninja skills, on the other hand, would be useful for protecting the Vocaloid characters from physical attacks.