Naisho no Tsubomi v01 tells the story of Tsubomi Tachibana, a fifth grader dealing with issues such as her mother's pregnancy, her first period, and the strange feelings she has started to get when she has been around boys.<br /><br />Naisho no Tsubomi v02 tells the story of Tsubomi Kusakabe, a fifth grader, who encounters an alien wanting to do research of earth. It turns out he has picked Tsubomi to be his research subject.