Sure, Karasuno beats Shiratorizawa in the manga. The match is full of thrilling moments and showcases the growth and determination of the Karasuno team.
Kageyama stays with Karasuno in the manga. His character development and contributions to the team continue without him leaving. The bond he forms with his teammates keeps him committed to the club.
Captain America would probably be very reflective. He might see his past self as a reminder of his long journey and how much he has changed. He could try to offer some words of wisdom to his younger self.
Some gods might be entertained. For instance, Hermes, being the trickster god, might enjoy seeing the different and often humorous takes on the gods in the fanfiction.
Issei could be a bit nervous at first. He might worry about what his classmates will think. But if they show positive reactions, he could become more confident and start sharing more about his writing. However, if they react negatively, he may feel a bit down and might even regret that they saw it.
Ryosuke would likely analyze the situation. He'd study his past self to see how he could have improved even more in the past. He might be a bit critical at first, but then realize that his past self was on the right track and that all the experiences he had, both good and bad, led him to become the racer he is in the present. He might also be curious about how his past self would react to his current racing skills and knowledge.
Spider - Man fanfiction often showcases the creativity of the fans. For instance, there are fanfictions that put Spider - Man in crossovers with other superheroes or even in different historical settings. I think it's a great way for fans to express their love for the character and expand on the Spider - Man universe that we know from the comics and movies.