One of the biggest omissions in Japanese textbooks, classes and one-on-one lessons is gendered language. Ignore it and at some point you will wind up sounding like a little Japanese girl — or a guy — when you didn’t intend too.
What exactly is “gendered language”? This refers to how males and females speak differently from one another within a language. It is a feature of other languages (Spanish, for one), but the Japanese version differs as it refers to gender roles and is not “grammatically gendered” — meaning that if you are a boy and speak like a girl, there is nothing grammatically incorrect about it. You would just sound like a girl, and that’s no fun.