Synopsis: Gakkou to Bed ja Seihantai no, Okkina Kanojo.

My Big Girlfriend Acts the Polar Opposite in Bed and at School. / My Big Girlfriend is Different in Bed than at School / 学校とベッドじゃ正反対の、おっきなカノジョ。Gakkou to Bed ja Seihantai no, Okki na Kanojo. An oneeshota-style doujin manga about a large girl and a similarly aged but much smaller guy. (Source: DLsite)