I am having a hard time understanding how they go to buy an anti-viral ''in masse'' just because the weather is colder. An anti-viral is to being used if one actually manages to catch a virus, like influenza, but getting a medicine expecting to get ill instead of taking precaution to not get ill sounds stupid. Even though many people tend to treat medicine as both miracles and an everyday prodcut even if that is bad for their health it cannot explain this. There is also that if not taking a look at a translation it looks like they are going to drink some cups to feel warm inside.
Another thing that puzzles me is that he is calling Arai with -chan, which is usually for women, and female or cute kids. I could expect -kun, but -chan ... , there has to be an use of the word which i am missing.