「Senpai, you dropped this.」
That sudden call marked the beginning of a relationship of an aloof senpai and his cute overenthusiastic kouhai-chan. Despite not having any contact previously except for using the same train station to get to school, senpai unwillingly agreed to a promise: from that day on, they would have to answer one question every day no matter what it was without telling any lie.
The disinterested senpai who doesn’t want to give up on his peaceful commuting time, and the passionate kouhai-chan who doesn’t want to give up on the only student taking the same train as her. This is the story of how their relationship will progress with just one question a day.