Maybe the OC gamer is a transfer student who discovers that the devils, angels, and fallen angels in the High School DxD universe have a secret gaming tournament. And the OC has to compete using their unique gaming skills and unlock new abilities along the way.
One idea could be an OC who is a gamer in the High School DxD world and uses their gaming knowledge to strategize in battles. For example, they might use their understanding of RPG leveling systems to level up their own powers faster than others.
A possible plot is that the OC is a misfit who doesn't fit into the typical categories in the High School DxD world. They might be a human with no obvious supernatural powers at first, but through their wits and determination, they manage to form alliances with different factions. They could use their knowledge of human technology and psychology to gain an edge, and along the way, they develop a unique power or ability that no one expected.
Well, perhaps the cheat allows the character to level up at an extraordinary rate in the Rating Game. This would completely disrupt the normal balance of power in the story. They might face challenges from both friends and foes due to this rapid ascension.
One idea could be an OC who is a gamer and discovers a hidden power within the Highschool DxD universe while playing a virtual reality game related to it. This power could be something unique like the ability to control shadows in the DxD world.
An interesting plot could be an OC gamer who is known for their role - playing skills in the human world. When they enter the Highschool DxD world, they start to role - play as a powerful being. This act fools many of the characters at first, but as time goes on, they have to actually become strong to keep up the facade and end up changing the power dynamics in the DxD world.
One idea could be an OC with a unique gaming ability that allows them to level up their magic skills faster in the DxD world. For example, they could have a 'gaming HUD' that shows hidden stats of enemies, giving them an edge in battles.
Well, a plot could involve an OC who is a gamer and a big fan of Dxd. They end up in a junkyard where they accidentally open a portal to the Dxd realm. Since they are a gamer, they quickly adapt to the new world and use their gaming skills to become OP. They could start by forming alliances with different factions in the Dxd world and use their junkyard - found items as unique weapons or tools.
A plot could involve Kaido being sent on a special mission by the Devil King to infiltrate a human school. During this, he starts to develop real friendships with the characters in High School DxD. His initial motives are questioned as he begins to care more about his new friends than his mission, creating a lot of internal conflict.
One idea could be a Dragonborn character arriving in the High School DxD world and having to adapt to the unique school and supernatural environment. They might use their dragonborn abilities to stand out in the Rating Games.
One plot idea could be that Naruto is summoned to the High School DxD world by a powerful magic user who mistakes him for a powerful demon. Once there, Naruto has to prove that he is not a threat while also trying to find a way back home. Along the way, he befriends some of the students at the school and helps them with their own problems, like protecting the school from a sudden attack by a group of rogue devils.
Well, in 'high school dxd torture fanfiction', a plot could involve a character being physically tortured in a magical prison where the pain is amplified by dark magic. This could lead to the character having to find inner strength and allies to escape. Also, perhaps a character is tortured by being isolated from their friends and loved ones, which is a form of emotional torture.