It might focus on Naruto and an antagonist who is deeply entrenched in the darkness. This antagonist could be a new character or an existing one from the Naruto series who has turned to the dark side. Other main characters could be the members of Naruto's team, who support him in his journey to understand and combat the darkness. They could provide different perspectives on how to deal with the dark elements in the story.
Obviously Naruto would be one of the main characters. He is the central figure around whom the'seeing red' concept is likely based. There may also be his friends like Sasuke and Sakura, as they are often involved in Naruto's storylines and could be part of the events that make him see red.
I'm not sure specifically as there could be many different fanfics with that title. Generally, it might involve Naruto characters experiencing or confronting some form of darkness, perhaps related to the darker aspects of the ninja world like the Akatsuki's actions, or personal traumas of the characters.
Since I haven't read it, I can't say for sure. But it could feature Naruto as a main character, as he is often central in many 'Naruto' fanfics. He might be the one guiding or inspiring the character who is rising from the darkness. Or it could be an original character created specifically for this fanfic who is on their own journey of self - discovery and redemption.
Most likely Naruto and Sasuke would be main characters as they are central in the original Naruto series and their stories can be easily explored in terms of having a 'dark side'.
It's difficult to say without reading the 'a taste of darkness fanfic'. However, it's common for fanfics to either focus on the original protagonists and give them new challenges related to the darkness theme, or introduce new characters that are embodiments of the darkness. For instance, if it's a fanfic based on a superhero story, the main characters could be the superhero facing a new, more menacing villain who represents pure darkness, or it could be about the superhero's sidekick who gets lured into the dark side and becomes a central character in this darker narrative.
Often, there is a brave hero or heroine who stands against the darkness. They might be an ordinary person at first but discovers they have some special power or ability.
There might be a character who is an expert in a particular field relevant to survival, like a former military person with combat and survival training. And there could also be a more vulnerable character, perhaps a young person or someone with a disability, who the group has to protect. This would add an extra layer of complexity to the story and the relationships between the characters.
Well, Naruto is surely a main character. And depending on the plot, characters like Kakashi could be important. He's Naruto's teacher and might try to guide Naruto away from the allure of darkness. Also, Orochimaru could be a key figure. He's always been associated with dark arts in the Naruto series, and in this fanfiction, he might play a role in Naruto's exploration of the darkness, either as an ally or an enemy.
The main characters would surely include Naruto. Then, depending on the direction of the fanfiction, characters like Jiraiya could be important as he might be the one to help Naruto understand and control his dark side. There could also be some dark - themed characters that are part of Naruto's heritage or the source of his 'son of darkness' status. And of course, his friends, even if they are initially wary of him, would still be key characters as they react to Naruto's transformation or discovery of his new identity.
Most likely Naruto would be one of the main characters. Depending on the crossover, it could also include characters from the other franchise involved in the crossover.