I thought yankee was more like... a punk. Not a really a delinquent but just someone who lives by their own rules. Not really sure how to describe it. Correct me if I am wrong.
You're not wrong, especially on the "not really sure how to describe it." The analogy to hipster and emo still holds, in that it'll mean slightly different things to different people, depending on where you are, who you're talking to, and how you feel about the style. A person who chooses to describe themselves as a Yankee would probably not include "delinquent," while a very strict teacher probably wouldn't get much farther than "delinquent."
Ichi-san from the Yankee days. Yankee is Japanese slang for a kind of juvenile delinquent. Like hipster or emo, it implies a certain fashion style in addition to an attitude. This is it. It's also rather old and out of style