Let’s learn Japanese with manga. What you are going to learn on this page is:
よくないっ!!
よくないっ
(Not good)
よくない is the plain present negative form of いい which means ‘good’.
You can tell that the person is quite upset with っ at the end.
【Japanese Grammar: Form】Polite Form and Plain Form for adjectives
There are two ways to say 'yummy' in Japanese for example. One is for talking with friends and the other is for talking with teachers and elderly people.