Conflict is a major theme. When Issei crosses over into another universe, there are bound to be conflicts, whether it's against villains from that universe or differences in ideology with the characters there. For instance, in a crossover with 'Attack on Titan', Issei might have to deal with the Titans and also the complex political and moral issues within the Walls. And of course, there's always the theme of survival as he faces new and dangerous situations in the crossover.
Romance can also be a theme. In some issei crossover fanfictions, he might develop relationships with characters from the crossed - over world. For instance, in a crossover with a magical girl anime world, he could end up having a romantic interest in one of the magical girl characters, which then adds an extra layer of story - telling as he tries to balance his feelings with his mission or place in the new world.
Power - up is a common theme. Since Naruto is godlike, it usually involves him having super - enhanced powers in the Sekirei world. Another theme could be relationship building, like how he interacts with the Sekirei characters.
Power - up is a very common theme. Naruto becomes extremely powerful, often to the point of being godlike. Another theme is the exploration of different universes. Since it's a multi - crossover, he gets to interact with different characters and settings from other fictional worlds.
One of the main themes is identity. When Alex Mercer is in a crossover situation, especially in a godlike form, his identity can be challenged or enhanced. There's also the theme of morality. His actions in a new, different setting might be questioned in terms of right and wrong. And of course, the theme of discovery as he explores the new world he's in. For example, if he crosses over into a fantasy world, he has to discover how magic works and how it affects him. These themes often interact with each other to create complex and interesting stories.
One common theme is power and its consequences. Since Shirou has godlike powers in these fanfictions, it often explores how such great power affects him, whether it corrupts him or makes him a better person.
Power. Since Naruto is becoming godlike or immortal, the exploration of extreme power is a big theme. How he uses it, whether for good or bad.
Power - scaling is a common theme. Since Naruto is godlike, the fanfics often explore how his overpowered abilities compare to the characters in the crossover world. Another theme is adaptation, like how Naruto adapts to a new and different universe.
One common theme is the exploration of new worlds. Since it's a crossover, Lara Croft might end up in a world she's never been in before, like a science - fiction universe. Another theme is power dynamics. With her 'godlike' abilities, she has to figure out how to interact with the existing power structures in the crossover world.
Often, a 'godlike issei' in fanfiction is depicted as having a more dominant personality. He may be more confident and in control, whether it's in battle or in relationships. His appearance might also change, with a more imposing or even divine - like aura. Maybe he has glowing eyes or a more muscular physique to match his new - found god - like status. He could also have a deeper connection to the supernatural elements of the story's world, being able to access and control powers that were previously unknown or unavailable.
One common theme is the clash of cultures. Naruto's ninja world has its own set of values and abilities, and the Assassin's Creed world has its own lore and rules. Another theme is power - how Naruto's 'godlike' powers change the power balance in the Assassin's Creed world.