The 'akaza sad story' might refer to the tragic backstory of Akaza from Demon Slayer. Akaza was once a human with a strong will. He had a family and a normal life, but due to various misfortunes and being turned into a demon against his will, he lost his humanity and was forced to do cruel things. He also had a lot of inner struggles as he still retained some of his human emotions deep down, which made his story a sad one.
Well, Akaza, originally Hakuji. He was a kind - hearted young man at first. He got involved with some bad people who took advantage of his situation. His love for the girl was pure, but they couldn't be together. When he became a demon, he lost some of his human memories but not all. His back story is full of pain and loss, which in a way, shapes his character as a demon. He is a complex character with a past that has both human and demonic elements intertwined.
One key element is his human life as Hakuji. His poverty and his attempts to care for his father are important. Another is his love for the girl, which was a major part of his human existence. And of course, his transformation into a demon due to the misdeeds of others towards him.
He would probably be quite amused by some of his past antics. For example, his constant pranks on Iruka-sensei. But at the same time, he'd also see the pain he carried from not having his parents and realize how that influenced his actions. He might react with a bit of regret for some of the stupid things he did out of loneliness, but also be glad that those experiences made him who he is today.
Well, some past gods might be amused. They'd see these modern interpretations of their stories and characters in the Percy Jackson fanfiction as a strange yet interesting new form of worship or at least attention. For example, Zeus might be a bit irked at some of the liberties taken with his character, but also secretly flattered that people are still so interested in him.
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.
Well, Boruto could be very inspired. Naruto's past is full of struggles, from not having parents around to being constantly underestimated. When Boruto discovers this in the fanfiction, he might realize that his own problems are not as big as he thought. He could be motivated to work harder and not take for granted the things he has, seeing how much Naruto had to fight for everything.
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.