If Ichigo becomes a vampire in fanfiction, he might gain enhanced physical abilities like super strength and speed. His appearance could also change, perhaps with paler skin and redder eyes. His relationship with his friends might be strained as they might fear or be suspicious of his new vampiric nature.
His character could become more solitary. As a vampire, he may feel isolated from his human friends and comrades. He might also become more aggressive due to the vampiric instincts.
Love is a very common theme. Often, there's a romantic relationship between Ichigo and a vampire character, which is full of passion and conflict. Another common theme is power. Ichigo's new - found vampire powers and how he uses or struggles with them is frequently explored.
A possible plot could be that a powerful artifact in the Rosario Vampire world is being targeted by both Hollows and some rogue vampires. Ichigo and Tsukune find themselves on a quest to protect it. Along the way, they encounter various challenges and meet different characters from both universes. The cultural shock between Ichigo's world of Soul Reapers and Tsukune's world of monsters and humans could also add some comedic and interesting elements to the story.
One possible scenario could be that Finn, after being turned into a vampire, struggles with his new identity. He might have to deal with the urge to drink blood while still holding onto his old values. For example, he could try to find alternative ways to satisfy his thirst that don't involve harming humans, like drinking animal blood.
One idea could be that Stiles is turned into a vampire against his will. Maybe he's attacked one night while out investigating something supernatural. As a vampire, he has to struggle with his new urges, like the thirst for blood, while still trying to be the same person his friends know. He might start to see the world in a different light, both literally and metaphorically, as his vampire senses heighten.
One possible story could be that Mimiko is bitten by a mysterious vampire one night while walking alone. She then starts to experience strange cravings and enhanced senses. At first, she's terrified, but as time goes on, she begins to embrace her new vampiric nature.
One common plotline is the transformation. For example, Ichigo might be turned into a vampire and has to deal with his new powers and instincts while still maintaining his relationship with Rukia. This can lead to a lot of internal conflict as he struggles between his human side and his new vampiric nature.
The theme of self - discovery is also prevalent. Ichigo has to figure out what it means to be a vampire lord, his place in the vampire world, and how to balance his new life with his old one. He often goes through a journey of self - exploration and growth in these fanfictions.
The Soul Reapers could be antagonists if they view Ichigo's vampirism as a threat to the balance between the living and the dead. They might try to hunt him down to eliminate this new, unregulated force.