Sakon and Ukon could develop from being ruthless and self - centered to more empathetic characters. For example, Naruto's positive attitude might start to rub off on them, making them question their previous way of life.
One possible plot could be Naruto discovers he has the Ukon Sakon Genkai in a moment of extreme danger. He then has to quickly learn to control it. Maybe at first he struggles with the dark aspects of this power, but eventually he masters it and uses it to defeat a powerful enemy.
At first, Naruto might be a bit confused and scared about having this Genkai. But as he explores its abilities, his confidence would grow. He could use the unique powers of the Ukon Sakon Genkai to his advantage in battles, and this would make him a more formidable ninja. His relationships with his friends might also change. Some might be in awe of his new power, while others might worry about him. Naruto would have to work hard to assure them that he's still the same Naruto at heart.
Another idea is a story set in an alternate universe where Sakon and Ukon are raised as ninjas in Konoha. Naruto befriends them early on, and they go through the ninja academy together. Their unique abilities would make for some interesting training scenarios and missions.
Jack was a man who was rather sly and liked to play tricks. He made a deal with the Devil and through his wits, he managed to avoid being claimed by the Devil immediately. But his actions led to him being barred from both Heaven and Hell.
In the 'Stingy Jack Story', Stingy Jack was a character who was both stingy and sly. He had the nerve to trick the Devil, which shows his audacity. He was not a moral person as his actions were mostly self - serving. His character is central to the story as his fate after death, being stuck between Heaven and Hell, is what the story is mainly about.
A prevalent theme is also their growth as individuals. Fanfictions may show how they develop their skills and personalities over time. For example, they might start as inexperienced musicians and grow into superstars. And of course, the theme of adventure can be found in some, where they embark on exciting trips or experiences together.
Texas Jack might have been a character with a reputation in the community. He could have been a frontiersman, someone who was among the first to explore and settle in certain areas of Texas. He might have been involved in building relationships with Native Americans or in establishing trade routes. There are many possibilities.
In the Jack the Ripper story, Jack the Ripper was a very infamous figure. He preyed on women in a poor area of London. There have been many suspects proposed over time, from local butchers to members of the upper class trying to cover up some sordid secrets. But no one has been definitively proven to be him.