Shinichi X Sera!

[MrDetective]

it's possible, I guess.
the thing is, there are way too many girls that like Shinichi/Conan. Haibara, Ayumi (although it's not true love or anything) and Ran.

lol have you ever watched a harem anime

[MeiTanteixX]

I have mentioned this theory before, and much of what is said here is something I agree with, but there is one thing(that i mentioned before) that strongly reveals this case to be true, judging by gosho's typical style of hinting the direction of where stories or characters are headed. In sera's introduction episode, the moment before she appeared sonoko said this to ran when they were talking about shinichi's indirect confession: "who knows, maybe a love rival might appear"...
That's a typical gosho(and not just gosho) style of giving away hints for upcoming events, ...

[nsa]

I really think Sera x Conan is going on. Like Meitantei mentioned, it is hinted in the first appearance of Sera that Sonoko said to Ran about rival might be coming.
And in the end of the Cold Case, she said to herself, I guess I'm a bad kid after all, because she saw how close Ran and Conan are, and she don't really want to ruin what they have by getting in the way of them both. Of course she knows Conan/Shinichi identity from the childhood memories of them she had remembered.
But she can't really help it around Conan, because Ran didn't know Conan's identity, Sera seems openly flirting with Conan just a guess though, but this is so exciting.