Yes, there are some great ones. You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Goku Highschool DxD' and you'll find a variety of stories with different plotlines and interpretations.
Well, there are several common themes. First, there's the clash of cultures. Goku comes from a very different background than the characters in Highschool DxD, so how they interact and understand each other is a big part of many stories. Then there's the theme of self - discovery. Goku might discover new aspects of his powers or his personality while in this new world. Additionally, the idea of protecting the new world he's in is also quite common. Since he has a heroic nature, he would likely want to keep the Highschool DxD world safe from any threats, whether they're new to him or familiar from his own universe.
Goku's powers in a High School DxD fanfiction would be a game - changer. His ki attacks could be on a level that could potentially destroy entire areas in the DxD universe. His martial arts skills are also top - notch. In a fight, he would use his speed and agility to dodge attacks and then counter with his powerful punches and kicks. His transformation abilities, like Super Saiyan, would be a shock to the characters in DxD. They might not have any means to counter such a huge boost in power.
It could be a really exciting story. Goku's godlike powers in the world of Highschool DxD would surely disrupt the power balance. He might introduce new fighting styles and values to the characters in DxD. For example, his Saiyan pride and never - give - up attitude could inspire the devils, angels, and fallen angels in that universe. Maybe he'd end up being a mentor figure to Issei or other main characters, teaching them how to reach new levels of power through training and self - discovery.
Goku would fit in as a super - powerful outsider. His physical strength and combat skills are far beyond what the normal characters in Highschool DxD are used to. He could become a sort of protector for the school, using his powers to fend off any threats that come their way. His energy - sensing ability would give him an edge in detecting hidden enemies.
Goku Black could potentially enter the High School DxD world through a dimensional rift or some sort of magical accident. Once there, his Saiyan pride and his dark motives (from his own story) could lead to him either trying to take over the various factions in the DxD world or simply looking for a worthy opponent. He might interact with the main characters like Issei, perhaps seeing him as a target to prove his superiority or a potential ally in his own schemes.
Goku Black might become a sort of anti - hero. He has his own sense of justice (albeit a twisted one in his original story). In the High School DxD world, he could oppose some of the more corrupt elements of the different factions while also causing trouble for the main characters as they try to figure out his motives. For instance, he could see the way some devils treat humans in the DxD world and decide to take matters into his own hands, but not in a way that the main characters would necessarily approve of at first.
Goku could have some interesting interactions. He might befriend Issei for his determination. Goku, being a pure - hearted fighter, would probably respect Issei's will to get stronger. He could also have friendly rivalries with some of the stronger devils or angels, challenging them to friendly spars to test their strength.
Xiao En was described as a Level Nine master in the TV series " Celebrating Years." Even though he had taken poison for twenty years and was seriously injured, he could still fight with other experts. Therefore, it could be confirmed that Xiao En's combat strength was at least at the ninth rank. However, it was impossible to determine if he was the strongest Level Nine expert.