There could be a plotline where a new and powerful enemy emerges in the High School DxD world and challenges the main characters to a death battle. The main characters then have to team up in unexpected ways and develop new strategies to defeat this enemy. This kind of plotline can explore the relationships between the characters further and also show their growth as they face a seemingly unbeatable foe.
A plotline where the characters from High School DxD are pitted against characters from other similar anime in death battles. Say, Issei against Ichigo from Bleach. This would be exciting as it combines the unique powers and fighting styles of two different anime universes, and fans can speculate on who would win based on their abilities and growth throughout their respective series.
One interesting story could be where the characters from Highschool DxD are really intrigued by the unique battle scenarios in Death Battle fanfiction. They might comment on the creative ways characters are pitted against each other, like how they'd compare their own powers to those in the fanfictions.
Perhaps in a fanfiction, Issei's death is part of a grander scheme. There could be an evil force that manipulated events to cause his death, thinking it would lead to chaos. But instead, his death unites the various factions in the Highschool DxD universe. They come together to fight against this common enemy that caused Issei's death, and in the process, discover new powers and alliances.
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.
Perhaps a plotline where the characters in the harem form a sort of alliance to protect Ophis from other threats in the 'Highschool DxD' universe. They could train together and develop new powers or abilities.
A plot could revolve around Issei and Irina getting lost in a magical forest. In this forest, there are all kinds of magical creatures. They have to find their way out while also helping some of the creatures they meet. This adventure would bring them closer together as they share many new experiences.
One concept that stands out in 'death reborn highschool dxd fanfiction' is the potential for character redemption through death and rebirth. A character who has made mistakes or been on the wrong side could be given a second chance via this process. They could then use their new - found life to make amends, which would add depth and complexity to the overall narrative.
One interesting concept could be the exploration of different character arcs in a death and rebirth scenario. For example, how a character's personality might change after experiencing death and coming back. Another could be the new powers or abilities they gain during this process, which can add a whole new dimension to the story.
Vali is also a likely winner in many scenarios. His Divine Dividing ability gives him an edge in combat, being able to halve his opponent's power and double his own. In a death battle, this could be a game - changer.
Another plotline could be a death battle where a character from RWBY has to fight an alternate version of themselves. It would be a psychological and physical battle as they grapple with their own strengths and weaknesses in a different form.
One interesting plotline could be Issei and Ophis going on a journey to discover more about Ophis' past powers. Since Ophis is such a powerful being, exploring her origins while in a relationship with Issei can add depth. For example, they might encounter ancient beings who knew Ophis when she was first created.