I think it's just because there's a specific word in Japanese that means "over 12 years", so it's easier to say. I haven't read the raws so I'm not sure if it's the one used but I'm betting on it.
In fact it's the same with english with "dozen". I'm not sure what your problem with the wording is. Maybe it's the translation choice. If it was worded "we're over a dozen years apart" would it change the effect on you?
correction: there's a term that means "12 years" I mean.
it's δΈεγ in case you're wondering
I mean if they wanted to use that phrase so bad they could've just made it 12 years. But I guess then it would've been too similar to other age gap incest manga lmao, because that seems to be mangaka's favourite age gap
Why is the author being so cagey with that "over 12 years"? If you can't say t with your whole chest, why not make the age gap smaller than 12 years???
It's 15! If he's a 1st year in college and he didn't skip a year to study he's 18. And he's 19 at most anyway, because he wasn't allowed to drink yet!
And this story still would've worked the same if it had been 12 years instead of 15.
Hell, it even would've worked with 8 years.
Anyway, I think the mangaka is a coward