One common theme is the exploration of their hidden love. Since Shinichi is often in his Conan form, there's a lot of unspoken tension and longing between them in these fanfictions. Another theme is teamwork in solving mysteries. They often work together to crack cases, and this shows their strong bond.
I also like 'Ran and Shinichi: Beyond the Mystery'. This fanfiction not only focuses on their relationship but also on how they grow as individuals. It shows Ran becoming more independent and Shinichi learning to balance his detective work with his personal life, all while their relationship blossoms.
In a fanfiction, perhaps Shinichi and Ran are on a school trip. They get separated from the group and find themselves in a beautiful, secluded spot. Shinichi looks at Ran, realizes how much he loves her, and leans in for a gentle kiss. This simple yet profound moment could be a turning point in their relationship, with Ran finally getting the affection she has been longing for from Shinichi all this time.
The popularity of Detective Conan x Ran fanfictions lies in the strong existing relationship between the two characters in the original series. Fans are always curious about how their relationship could develop further, like if Ran will finally figure out Conan's true identity. Also, the mystery and adventure elements in the original show can be carried over into the fanfictions in unique ways.
One great Detective Conan x Ran fanfiction is 'A New Adventure for Conan and Ran'. It shows a different side of their relationship during a mystery in an old castle. Another one could be 'Ran's Discovery' which delves into how Ran might find out Conan's true identity in a really unique way. There's also 'Conan and Ran: A Future Together' that speculates on their future relationship after Conan reveals his identity.
Conan would be extremely determined. He'd immediately start investigating. His first reaction would be to figure out who could have a motive to kidnap Ran. He'd think about any enemies he has made as Shinichi, since they might target Ran to get to him.
In many Detective Conan fanfictions, a kiss between Shinichi and Ran is a highly anticipated and emotional moment. Some fanfictions might have this happen during a dangerous situation where they think they might not make it out alive. For example, when they are trapped by a villain and in that moment of despair and love, they share a kiss. It's a way for fans to explore the romantic side of their relationship that is often hinted at but not fully realized in the original series.
Romance is a big theme as well. Writers explore the relationship between Conan and Ran in different ways, from the angst of Conan hiding his true identity while still having feelings for Ran, to more fluffy and sweet relationship developments.
One of the common themes is trust. Ran has to trust that Shinichi will come back to her, and Shinichi has to trust Ran with his secrets. Also, the theme of sacrifice comes up. For example, Shinichi might sacrifice his own safety or time to protect Ran. And of course, the theme of reunion is also there, as they are constantly in a state of being apart and then coming back together.
If it's a well - written fanfiction, there could be some unexpected twists. Maybe the kidnapper is someone Ran knows, like an old acquaintance with a grudge. Or perhaps there are multiple kidnappers with different goals. Conan would not only have to deal with finding Ran but also with any traps or false leads set by the kidnappers. And Ran, being a strong - willed character, might try to escape on her own, leaving behind some clues for Conan to find.