I don't really understand why the Japanese do this, because it's not like the reality of love in Japan is being awkward and tip-toeing around telling people you're interested in them or love them... but at least in their writing, especially in regards to manga, they characterize love as forbidden and sex as forbidden and the only acceptable measure of reaching the status of potentially loving someone being strange and awkward and roundabout.
Surely, instead of making both of you feel uncomfortable, you could just say, 'I like you, let's date.' But even here, once the characters accept their love for each other, the only acceptable way for them to be intimate is on the other side of some abstract dimension apart from physical reality. Y'know if being physically intimate was that obscene, we at large, wouldn't do it, right?
It would be sinful and against God and wouldn't be innate. (And from the perspective that God isn't real but a concotion of man as an abstraction and holder of innate virtue - man invented God, so why would he not include in His sense of virtue the primal instinct and flame of life, reproduction?)
In reality, physical intimacy is the most connected you can be with another person and is the most emotionally affective. Getting a hug can turn your whole day around. It can solve any trivial fight with someone that might otherwise nap at you for days. Heartfelt physical intimacy is a fundamental aspect of being human and the rejection of it is the rejection of your own humanity. So, why the Japanese feel suffering intrinsic to love is beyond me.
Fiction is an image of reality, sometimes only a sliver thereof, but the prevalence of this idea in manga makes it seem a real idea in the Japanese conscious. Yet, I hope the simplest explanation is true: that this observed, forced, estranged, pained method of love, is a result of editorial censorship to patronize children while attempting to maintain the outline of an idea, and not some intrinsic aspect of the Japanese mind.