In fanfics, anything is possible. Since it's a fictional creation, an author could write a scenario where Naruto has the ability to use Bankai. However, in the original Naruto and Bleach universes, their powers are completely separate, with Naruto having chakra - based ninja abilities and Bankai being a high - level power in the Bleach world.
Naruto's bankai might incorporate his fox - like features. Given his connection to the Nine - Tails, his bankai could have a large, fiery fox form that enhances his speed and strength, much like how his Nine - Tails Chakra Mode works. His zanpakuto could also be related to the rasengan, perhaps having the ability to fire off rasengan - like attacks from the blade or using the spinning energy as a defensive mechanism.
Naruto might use Bankai in a more physical and direct way compared to Bleach characters. Since Naruto is used to combat with his body and chakra - enhanced attacks, his Bankai could be more like a physical transformation rather than the more spiritual manifestations in Bleach. For example, instead of a spectral form, his Bankai could be a physical enhancement of his body with the Zanpakuto's power.
One interesting 'Naruto Senbonzakura Bankai' fanfiction could be one where Naruto somehow gains the power of Senbonzakura Bankai and has to learn to control it. He might face off against powerful enemies in new and unexpected ways, using the unique abilities of the Bankai.
In a Naruto achieves bankai fanfiction, it could happen through some sort of cross - over magic. Maybe a powerful jutsu misfires and transports Naruto to the Bleach universe where he somehow gains the ability to achieve bankai. It could also be due to a powerful being bestowing this power upon him in an attempt to create a powerful ally or as part of a grand experiment.
One popular bankai ichiruki fanfic might be those that explore their unique bond during intense battles. For example, some stories could focus on how Ichigo's bankai development is intertwined with his relationship with Rukia. They might show how their powers complement each other in ways not seen in the original series.
In fanfiction, it usually works by combining the elements of Naruto and the Senbonzakura Bankai from Bleach. For example, Naruto might be able to summon cherry blossom - like blades similar to how Senbonzakura Bankai works in Bleach. These blades could have special properties like being able to cut through chakra or being able to move at super - fast speeds.
First, study their characters well. Know Ichigo's impulsive yet determined nature and Rukia's calm and collected demeanor. Incorporate the concept of bankai in a way that makes sense for their growth. For example, Ichigo's bankai could evolve as a result of his feelings for Rukia.
It's hard to say exactly. Maybe there was a hidden plot twist or a secret they discovered that made them run. Maybe they were trying to avoid being caught by some villains. Without more details from the visual novel, it's tough to be certain.