Well, in that situation, Sirius would be shocked and heartbroken. He might first scold Harry for doing something so dangerous to himself. Then, being the impulsive person he can be, Sirius would probably take Harry to see someone he trusts, like Dumbledore or Madam Pomfrey. He would not let Harry out of his sight until he was sure Harry was okay and not likely to do it again.
Sirius catching Harry cutting in a fanfic would be a very intense moment. Sirius, having been through so much himself, would understand the pain that might lead to such an act. He would be gentle yet firm with Harry. He'd hold Harry, make sure the cuts were taken care of, and start to dig into what was wrong. He'd probably share some of his own experiences of dealing with pain and trauma, trying to make Harry realize that there are better ways to deal with whatever he's going through. Sirius would be Harry's rock in that moment, guiding him towards getting help and healing.
In a fanfic scenario, if Remus catches Harry cutting, he would likely be very concerned. Remus is a caring character. He might immediately try to stop Harry and find out what's wrong. He could use his calm and understanding nature to get Harry to open up about his troubles.
Sirius would be deeply affected. He'd see Harry as a sort of surrogate family, and seeing Harry in such a state would make him feel like he failed in protecting him. He'd do everything he could to make Harry feel better, from getting him medical help to just sitting and talking with him for hours about what's wrong.
One possibility is that Sirius could be initially shocked. But then, being the understanding person he is, he might give them his blessing. After all, he has seen how Harry has grown and Ginny is a great girl.
Well, if Sirius takes Harry to Voldemort in a fanfic, it would be a huge deviation from the normal story. One possibility is that Sirius is trying to make some sort of deal with Voldemort to save others. But Voldemort is not one to be trusted. Harry, being the Boy Who Lived, is a valuable asset to Voldemort for his own dark purposes. It could lead to a tense stand - off where Harry has to use his own wits and magic, even at such a young age, to try and escape the clutches of the Dark Lord.
In the fanfic, Sirius and Harry leaving England could lead them to a hidden magical island. There, Harry could learn different kinds of magic that are not taught at Hogwarts. Sirius would be able to protect Harry better as they are far away from the threats in England. They might also start a new life where Harry can grow up without the constant fear of Voldemort's followers finding him.
One possibility is that their meeting is a vision or a dream - like encounter. Harry could be drawn into Azkaban in his sleep or through a magical object. During this encounter, Sirius could give Harry advice on how to deal with the upcoming challenges at Hogwarts. He might warn Harry about certain people who can't be trusted and offer his insights on the growing dark forces.
In the fanfic, Absol might be in some kind of trouble that Ash has to rescue it from. After that, Absol decides to join Ash's team. Ash would then have to train Absol and figure out how to best utilize its skills. They could go on adventures together, facing various challenges and meeting new Pokémon along the way. Absol could also introduce Ash to new areas or Pokémon that are related to its own origin or habitat.
She might get detention. Snape is strict, and cutting class is a serious offense in Hogwarts. He could assign her to clean the potions classroom or help with sorting ingredients in the dungeon.
Sirius might confiscate whatever Harry was smoking. He would then sit Harry down and have a serious conversation about the importance of making good choices. He could also remind Harry of the dangerous magic substances that might be out there that are far worse than normal cigarettes and that he should stay away from any form of harmful substances.
Remus would be horrified. He'd probably quickly take the cutting tool away from Harry.