These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Epileptic Trees: The idea that Yuki might actually really be a female, and his mother was just mistaken or having a joke at Masato's expense or so on... basically, a lot of explanations for Yuki possibly actually being a girl. This is despite the fact that the manga has gone so far as to have Masato see Yuki naked and sitting in his lap at one point, and he still thinks Yuki's a guy.
Fan Wank: Some of the theories about Yuki "really" being biologically female can reach these levels. The manga was even encouraging some of the early fanwank, since even Masato wasn't sure Yuki was really biologically a male, and a couple of times tried to catch Yuki changing to verify it (although he either chickened out or was thwarted).
The Scrappy - Masato, due to the way he treats Yuki and Kaoru.