Sutoponi

"School comedy of female students who have hooters. They have special constitutions, so that when they have their hair done in a ponytail, they become athletes." Catchphrases were "a 4-koma comic strip of oppai has arrived!?," "supposed to be a story about girls who become athletes when they make put their hair up in a ponytail, but somehow, it became a manga about three female students who have big tits!?"

From Akibablog