It all started with Sakakibara Marika's remark, "There’s no way it could be between women." The hundred-day challenge with Fuwa Aya, betting a million yen, seemed to reach a happy ending with their mutual confessions before the deadline. However, to thoroughly settle the question of whether "it could be between women," the two decided to spend the fateful hundredth day on a hot spring trip as lovers…! Marika realizes that the days spent with Aya have changed her belief that it was "impossible." Can Marika, after a hundred days, still insist that it’s "impossible"?