It's hard to say it's a widely 'popular' genre in the traditional sense. While there may be some fans who explore such themes in fanfiction, it's not something that represents the mainstream of Splatoon fan works. The Splatoon series is mainly known for its unique gameplay and colorful characters, and most fanfiction focuses on things like character relationships, adventures in the Splatoon world, and interpretations of the game's lore. However, in the vast realm of fan-created content, there will always be a small subset of more niche or out - of - the - ordinary concepts like this.
Futanari fiction is a genre in fictional literature. It often involves characters with both male and female sexual characteristics. However, this genre contains adult and sexual content which is not suitable for all audiences.
The Splatoon manga is indeed canon. It contributes to the broader narrative and world-building of Splatoon. Any variations from other elements are usually intentional and part of the creative process to expand the story.
The story length of Splatoon 3 can vary depending on how quickly you progress and how much you explore. Generally, it can take several hours to complete the main story missions.
The length of the Splatoon 3 story can vary depending on how quickly you progress and your playstyle. But on average, it takes several hours to complete the main storyline.
I don't have the specific number off the top of my head. Maybe you can ask manga experts or do some research on manga review platforms to get a clear answer.