
There is no distinction between shoujo-ai and yuri. Those are BS classifications that have been made up by western fans (that they don't even really stick to) In Japan, shoujo-ai and yuri are interchangeable terms. If there is any distinction between them, it is maybe the age of the characters, but even that isn't consistent. This is why this website can never decide what to tag anything, because stories like this routinely shows up in books labelled or titled "Yuri" something, and more explicit stories are often labelled as shoujo ai. They're both just marketing terms for "this be gay, yo".
Some stories about romance are explicit, some aren't. Some stories show sexuality, some don't. They're all the same genre.
Just because the author decided to be subtle doesn't mean there isn't an explicitly romantic angle to this story. The author could have chosen "Anne of Green Gables" or any of a dozen other books about close friends in order to typify the relationship between these two girls, but they didn't. They chose Romeo and Juliet. If you don't read their relationship as romantic, you just aren't paying attention.

Hey, I understand your point.
I did assume things in order to simplify like
shoujo-ai= fluff, kinda romantic (like this one, I guess) while Yuri= may contain sex, more complicated plot.
But thanks for clarifying that cuz I thought their really is a distinction in Japan.
I think the problem with these tags is the way Japanese don't have clear sense of their 'genres' (and not making clear distinction, like this one). Like a manga's tags is based on the magazine they're being published, so even if a work is obviously a seinen (as we perceive it to be), it's tagged as shoujo (as in the case of Banana Fish). Then again they made that 'genres' so I guess they can be flexible about it for all I care (Yup, I'll stick to my labels *for my sanity).
Is the new Yuri now?