It's interesting that an ealier chapter said 80-90% of the (student) koto players are female, but when the series keeps introducing individual, named opponents, they are mostly guys. When it's female, it's the Himesaka koto club, which emphasized perfect unity, so no particular individual is the real opponent, even if Puff Head (Kazusa) is separated from the rest for being the Satowa fan. I wonder if this is because in traditional shounen manga the majority of the audience wants to see guys fight each other, or perhaps it's because the author, being a former shoujo mangaka, simply enjoys drawing and designing meaningful, individualistic male characters more.