Kodomo no hi <Children's Day>, 5 May, was originally Boys' Day, for which Kei is wearing an origami samurai helmet and carrying a koinobori, a sort of wind-sock decorated as a carp, symbolizing strength and preseverance
Tsuyu <the rainy season>, marks the advent of summer; it lasts a few weeks, long enough for the Japanese to refer to it as their "fifth season"
