These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Sumiyoshi: "No one knows more about Misaki than you do, Hiyama ... and vice-versa. Other than Misaki, the only person who knows as much about you is ... Yuuji, propably. Hiyama, you wanted Misaki to understand your feelings. But Misaki brushed you off. She's wrong there. But even if she does that, Hiyama, how could you turn your back on her? How could you not believe until the very end that she would understand. Isn't that what true friendship is all about?"
And after that Misaki and Kozue making up and Kozue informing Yuuji, that she is not afraid anymore to leave Japan as she knows her friends will always be there.
Genius Bonus: There are quizzes in-game with questions regarding classical Japanese literature and Mahjong. While there is no punishment for failing the first one, the second one is an important part of one of the routes.