A possible plot is that the SI gamer gets transported into the Highschool DxD world but discovers that their gaming skills are directly related to their magical abilities. So they start training like they would in a game, grinding levels by doing quests for different factions. They could also introduce new gaming - inspired spells or techniques that no one in the DxD world has seen before, which would make them a target for some and an ally for others.
The SI character could be a gamer who is actually a reincarnation of a powerful being in the Highschool DxD universe. Their gamer instincts help them recall their past life's knowledge and powers slowly. They then use this knowledge to not only become stronger but also to change the fate of some of the characters they befriend. For instance, they might prevent the death of a certain character by using their knowledge of future events from their gamer - like precognition skills.
One idea could be the SI (Self - Insert) character using their gamer knowledge to unlock unique powers in the Highschool DxD universe. For example, they might figure out a way to level - up their devil or angel abilities like in a game. Another plot could involve the SI character forming a special team with the existing characters in the series to compete in some sort of supernatural gaming tournament within the DxD world. This could bring in new challenges and alliances.
A possible plot is that a group of students in High School DxD start a gaming club, but they accidentally discover that the games they play are linked to some ancient and powerful magic. As they delve deeper into these games, they uncover secrets about their world and have to face off against enemies who want to use this magic for evil purposes.
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.
One idea could be a gamer who gets transported into the Highschool DxD world with godlike powers and uses his gaming knowledge to outwit the devils and angels. For example, he might use strategies from real - time strategy games to plan battles against his opponents in the new world.
One interesting plotline could be the main character using their gaming knowledge to gain unique abilities in the Highschool DxD world. For example, they might apply strategic thinking from games to outwit opponents in battles.
One idea could be a gamer who gets transported into the Highschool DxD world and uses his gaming skills to gain power and allies. For example, his knowledge of strategy games helps him in battles and political maneuvering within the devil, angel and fallen angel factions.
Another plot idea could be that the gamer character starts a 'game guild' within the Highschool DxD world. He recruits other characters from the series who have an interest in this new way of approaching the challenges in their world. Together, they embark on quests and missions, facing both in - school rivalries and otherworldly threats while using game - inspired teamwork and strategies.
One idea could be the self - insert (SI) character having a unique power that disrupts the power balance in the High School DxD world. For example, they might have the ability to nullify demonic or angelic powers temporarily. This would lead to various characters being intrigued or threatened by the SI.
One idea could be creating a new character who is a transfer student with a unique power. For example, a character who can manipulate time in the Highschool DxD universe. This could lead to all sorts of interesting plot twists, like changing the outcome of battles or getting a peek into the past of the main characters.