There is so much detail on this picture. "Maus" written on the mouse, the autographed tank model, "Shico Shico" brand tissues, the oppai drawing at the bottom of the math homework, etc. The phone has messages from Miho and from Mika, and I believe the doujin with two guys is of Yukari's dad and Hana's mom's servant, as it's called "Barber and Servant". That's Darjeeling on the doujin under that one, adding tag.

It has been forever since I studied it, but the homework looks like quantum mechanics stuff, so it's probably physics homework. I wonder if the "older" tag might apply because there is a beer can and the drinking age in Japan is 20.