One of the main themes is loyalty. In these fanfictions, they are usually shown to be extremely loyal to each other. No matter what challenges they face, they stand by each other. It could be against a common enemy or dealing with internal conflicts within their group. Also, the theme of discovery is present. Discovering new things about themselves and each other as their relationship progresses.
A common theme is the power dynamic. Alucard is often portrayed as very powerful, and Alexander might be more of a strategist. So, how they balance their strengths is a big theme. For example, in many stories, Alexander's plans are carried out with Alucard's brute force. Another theme is redemption. Maybe one of them has a dark past, and the other helps them find a new path.
One common theme is the exploration of their different natures. Since Bella is often portrayed as a more innocent or human - like character, and Alucard is a powerful vampire, there's a contrast. Another theme could be power dynamics, like how Bella might be influenced by Alucard's power or how she might change in his presence.
One common theme is power. Alucard is a very powerful character, so fanfictions often explore how he uses his power, how he gains more power, or how he struggles with the consequences of his power. Another theme is redemption. Given his often dark and violent past, many stories deal with Alucard seeking some form of redemption.
One common theme is the exploration of her power in a different gender context. For example, how she might use her vampiric abilities differently as a female. Another theme could be relationships, like romantic relationships with other characters in the Hellsing universe, which might be portrayed differently compared to when Alucard is male.
One frequent theme is the idea of identity. Harry, with his own identity as a wizard and the Boy Who Lived, has to grapple with Alucard's identity as a powerful vampire. Also, the theme of friendship or rivalry might be present. They could start as rivals due to their different natures but end up as friends who respect each other's abilities.
Power struggles are a common theme. Since Alucard is very powerful, when he crosses over into other universes, there are often clashes with powerful characters there. Another theme is the exploration of his identity. In different crossovers, his vampire nature and his moral compass are re - examined.
One common theme is power. Naruto has his ninja powers and Alucard has his vampiric powers. In the harem context, they often use these powers to protect the members of the harem. Another theme is loyalty. The members of the harem are usually loyal to Naruto and Alucard, and vice versa. Also, there's the theme of friendship. As they build the harem, Naruto and Alucard form new friendships with the characters in it.
One common theme is the exploration of their unspoken feelings. The kiss often serves as a way to finally break the ice and let their true emotions show. Another theme could be power dynamics. Alucard is much more powerful than Seras, and the kiss might be a moment where that power difference is either emphasized or ignored.
Another theme is identity. A female Alucard may struggle with her identity, especially when compared to the original male Alucard. She might question her place in the Hellsing organization and how she is perceived by others.
One common theme is the supernatural. Since Alucard is a supernatural being, the fanfictions often involve elements like vampires, magic, and the occult. For example, the reader might be a human who gets involved in Alucard's world of the supernatural.
A very frequent theme is the exploration of loyalty. Seras' loyalty to Alucard and vice versa is often a central aspect. Also, redemption is sometimes a theme. Seras may see Alucard as a means to redeem herself or find a new purpose, and Alucard might find some form of redemption through his relationship with Seras. It's a complex web of themes that make these fanfictions so interesting.