@Walter_vi_Britannia
I never got the correlation with coffee being adult like.
It's not that hard to understand, really.
Coffee is bitter. Because it's bitter, not a lot of kids drink it. Despite being bitter, lots of adults drink it. Therefore, drinking coffee makes you seem more mature.
Japan just likes to over dramatize certain stuff.
Please, they're kids.
No Japanese adult would think that drinking coffee makes you more adult-like.
It's a childish fantasy, just like "touching girls gives you cooties", or "smoking is cool", or similar such bullshit.
Anyway, mostly everybody drinks coffee with sugar in it. Nothing adult about drinking bitter coffee. Actually, the first thing people would assume if they saw you drinking coffee without sugar would be that you had diabetes. lol
And the Japanese are no different. In fact, canned coffee sold in Japan is significantly sweeter than anything you'd find in Europe or America.