Well, for 'the god of high school crossover fanfiction', you could do a crossover with a classic anime like 'Dragon Ball'. The high - energy battles in 'the god of high school' would blend well with the power - scaling and epic fights in 'Dragon Ball'. Or perhaps a crossover with 'Naruto'. The ninja skills and the unique power systems could interact in really cool ways. And a crossover with a magical girl anime could also be interesting. The male characters might have some unexpected reactions to the magical girl's powers and their cutesy world.
One idea could be to cross it with a superhero universe. Imagine the characters from 'the god of high school' getting superpowers and teaming up with well - known superheroes to fight a common enemy. Another idea is to crossover with a fantasy world like Middle - earth. The combat - loving characters would fit right in among the elves, dwarves and hobbits. A third idea could be a crossover with a post - apocalyptic setting, where their martial arts skills are put to the test in a world full of danger and chaos.
You could do a crossover with 'Sword Art Online'. The virtual reality aspect of SAO could be combined with the supernatural elements of High School DxD. For example, the characters could be trapped in a virtual world that has elements of both worlds, and they have to fight their way out. Issei might have to use his skills in a new digital environment while also dealing with SAO - like challenges.
Well, a cool crossover idea might be the sharing of powers. Imagine if some of the High School DxD characters could learn Naruto's shadow clone jutsu. It would be really useful in battles. Also, the idea of Naruto characters trying to understand the complex social hierarchy in DxD could be very entertaining. They could end up forming alliances in unexpected ways, like the ninjas teaming up with the devils to fight against a powerful demon from Naruto's world that has somehow entered the DxD realm.
One idea could be a crossover between 'High School Musical' and 'The Little Mermaid'. Imagine Ariel attending a human high school on land for a semester as part of a cultural exchange program. She could join the school's musical club and struggle with fitting in while also trying to keep her mermaid identity a secret. Another plot could involve characters from 'Beauty and the Beast' in a high school setting. Belle could be the new girl in a school full of jocks and popular kids, and the Beast could be a misunderstood loner. They might be paired together for a school project and slowly start to see each other in a new light.
A great plot could involve a tournament in the High School DxD world that Gohan participates in. He teams up with some of the characters from that series. His different fighting style and abilities would shock everyone. There could be some sort of mystery or conspiracy behind the tournament as well, and Gohan's integrity and sense of justice would drive him to uncover the truth.
Another idea is that there's a magic spell that mixes the worlds of Naruto and High School Musical. Characters like Sakura find themselves in the middle of a high - school musical competition. She uses her medical ninjutsu knowledge to help heal an injured singer from the High School Musical side. In return, they teach her some new singing and dancing skills which she then takes back to the ninja world.
One idea could be a crossover with 'Fate/stay night'. You could have the characters from High School DxD enter the Holy Grail War. Issei could use his boosted gear in new and exciting ways against the Servants. Another idea is a crossover with 'Naruto'. The ninjutsu from Naruto's world would be a cool addition to the battles in High School DxD. For example, Sasuke's Sharingan could create some interesting interactions with the devil eyes in DxD.
One idea could be a crossover with Norse mythology outside of the God of War series. For example, Kratos could meet Thor from the original Norse tales. Another could be a crossover with Greek and Roman mythology, where Kratos encounters some of the forgotten or lesser - known Roman gods. Maybe a crossover with a popular fantasy world like Middle - earth, and Kratos has to face off against some of the powerful beings there.
A crossover with another popular action - adventure game like 'The Witcher'. Geralt and Kratos could meet in a world that is a blend of their two universes. They might initially be at odds due to their different moral compasses, but then find common ground in fighting a powerful, otherworldly enemy that neither could defeat alone. This would create an interesting dynamic between their combat styles and personalities.
One idea could be a crossover with 'One Piece'. Imagine the Tower of God characters having to navigate the Grand Line. They might face off against pirates or team up with the Straw Hat crew. Another could be a crossover with 'Naruto'. Tower of God's Bam could learn ninjutsu from Naruto and use it in his climb up the tower. A third idea is a crossover with 'Fullmetal Alchemist'. The alchemical concepts could be introduced into the Tower of God universe, like how the alchemists might try to understand the tower's power system.
One idea could be that Goku is transported to the realm of the gods and has to participate in a divine tournament. He'd face off against powerful god - like beings using his Saiyan strength and martial arts skills. His Saiyan pride and determination would make him a formidable opponent even among the gods.