Ordo said:
Of COURSE Deku is oblivious to love...because, for whatever reason, God/evolution (Take your pick) decided that the Japanese male protagonist should be so dense about romance that the Japanese female has to take a hammer to their thick head to make them understand how said female feels. This way we weed out the passing crushes from the real loves.
It's the medium and the target audience.
Plus the culture has a bit to do with it.
If the protagonist ever gets wise and notices his crush likes him or actually makes a decision, the rom-com element of the series ends.
Plus, you've got to remember that the target audience for this stuff is roughly 12-16. They can't show graphic sex and even kissing is kind of borderline. Even implying sex is a bit far to be honest.
Then there's the culture. Japan is weird when it comes to stuff like that. Remember that the idea of "purity" is still a pretty big cultural factor. Much more so than it is in the west, especially regarding media like manga and anime, even more so with the age group they are going for.
Honestly, it's not really that different than the kind of romance we see in western media targeting that age group.
Nothing ever happens, one or the other probably doesn't notice the other likes them, and maybe a kiss on the cheek or holding hands is about as far as it goes, if it goes anywhere at all.