What emotions might Sasuke be experiencing while watching Naruto sleep in the fanfiction?

Well, it could be a complex mix of shock, anger, and betrayal. Shock because it's unexpected, anger towards the person doing the seducing, and betrayal as it involves one's spouse.

Well, Boruto might feel a sense of pride seeing his father Naruto in action against Sasuke. He has heard so many stories about their battles, and now seeing it in a fanfiction version could make him realize the deep bond and rivalry between them. He might also analyze their fighting styles and try to incorporate some of their moves into his own combat techniques later on.

He might feel anger. Since he was so set on revenge against Itachi, any portrayal that didn't match his view of himself as the victor could make him angry.

The character might be really intrigued. They could be thinking about how the fanfiction is changing or expanding the original Undertale story. Maybe they are comparing it to their own experiences in the Undertale world, if they are a character from that universe.

Love, definitely. Sora's sacrifice for Kairi is likely to be driven by deep love. Also, there could be sadness as the characters are separated in such a tragic way.

He might be really surprised. He could find it strange to see different versions of his own story and the people around him in the fanfiction.

She might be thinking about how the fanfiction either stays true to the original relationship dynamics between her and Naruto or how it changes in interesting ways.

He might be really amazed. He'd see different versions of his world and himself, which could make him think about his own life and choices in a whole new light.

Naruto might feel a bit of nostalgia. He would see elements of his own past and how the new generation, like Boruto, is being portrayed in these fictional stories. He could also be proud to see how much his son has inspired fans to write so many different stories.

Some characters might be amused. For example, Naruto himself could find it funny to see how others imagine his adventures in different ways. He might laugh at some of the out - of - character interpretations but also be intrigued by the creative storylines.