Shuugaku Ryokou de YouCha to Onaji Group ni Nacchatta Mekakure InCha-chan

On the school trip, the introverted, gloomy Kage-chan ends up in the same group as the extroverts... But the extroverts don't mind and just enjoy the trip together!! But at night, the extroverts start playing a "naughty game" that's unique to the extroverts. Kage-chan tries her best to keep up with the extroverts' vibe. But then, something unexpected happens to the extroverts: Contrary to her plain appearance, Kage-chan's body is damn sexy! The extroverts get their dicks rock hard upon seeing Kage-chan. Kage-chan's uterus throbs at the realization that he's arousing them. When their sexual desires reach their peak, it all begins... It's time to copulate! Mating, mating, mating!! And what awaits them after their passionate, devoured encounter... (Source: Fanza translated)