In general, Freezing manga doesn't have nudity. It focuses more on the action and story rather than such explicit content. The creators aim to maintain a certain level of propriety in their work.
Naruto himself is obviously a main character as it's in the Naruto universe. Sakura might also be a prominent character. She could be involved in the story either as Naruto's friend or love interest. Sasuke is another likely candidate. His cool and brooding nature could contrast well with Naruto's more exuberant personality in the context of the freezing lemon - themed story.
It could be written by fans of the original work that 'freezing' is related to. Maybe die - hard fans who love to explore different storylines and ideas within that particular universe.