First and foremost, this is a great OVA! I can't deny the fact that there are some parts that are unrealistic but despite that, it was actually the thing that made the romance great. Pointing out why this is a great OVA, it makes you ask yourself: Why Conan is doing this? Then your mind shows up images about Conan from how it started towards his adventure in retrieving his body back.
So, what I thought that were unrealistic are:
1) Who would freaking believe that the Black Organization which has Vermouth that knows Conan's true identity, not find him yet? I mean, even if I had a debt deep in my heart, it probably wouldn't last that long. Besides, there may be orders from the Boss to search for it, knowing Gin's character.
2) Is Ran and the other people that were related to Shinichi that has seen his face that stupid not to know that he is Shinichi, the Detective of the East? Surely, that's kind of creepy not knowing someone by appearance.
3) Is Ran really that stupid, compared to the others, after confessing in the library that he is Shinichi with his feelings? Ran didn't even believe Conan that he is Shinichi (although I doubt that)
4) I guess the romance stuff was too much. If I were Shinichi telling my childhood friend who eventually ended up with a relationship, I would explain things to her immediately instead of saying "I'm Shinichi, Ran," or "I'm not like him... I am him!" I'd say that but immediately follow it with an explanation.
Those were the details that I seem to have found out. xD
It may sound kind of offensive of me talking like that but remember, this is a great OVA and probably the greatest "romance stuff" in the series (excluding the said details).
Oh, and I was expecting it to be a little bit longer to know what Ran would end up saying about him saying that he is Shinichi... It's still stuck into my mind. It's as though I was watching it within 5 minutes. Dx
Surely, I can tell you that this is the greatest time-killer episode (20+-minute episode)!