Yoshino is saying that mainstream is a myth by stating that no mainstream actually exists. Our society can't achieve a mainstream person or expectation, because mainstream is subjective. A "normal" person to me isn't the same as a "normal" person to you, or my parents, or my neighbor, or the president or anyone else. The judgment of labeling someone normal becomes opinionated and one idea of mainstream will always differ from the next. Yoshino also addresses that by being mainstream you must achieve a quality of average accomplishment in every characteristic of life, and that too is unachievable.

I think he supports his argument well. He includes many situations involving many different kinds of people which makes his essay relatable to most readers. He talks about how everyone is trying to become normal but nobody can or will become this because it doesn't exist.

My idea of mainstream prior to reading this was someone who is average, typical, and in some cases perceived as boring. But after considering Yoshino's points, I think really mainstream is defined by the people who an individual considers mainstream and not by the ultimate community.