Als Riki nach einem Ball sucht, der im Baseball-Training verloren gegangen ist, trifft er auf Mio, ein Mädchen, das immer unter einem Sonnenschirm mit einem Buch in der Hand im Schatten eines Baumes zu finden ist. Es gibt ein Buch, an dem sie besonders hängt, aber sie will Riki nicht erzählen, wovon es handelt. Als sie dieses Buch verliert, liegt es an Riki, ihr bei der Suche zu helfen.
Riki is tasked with finding the last member of the Little Busters to have a full baseball team of nine. Riki hits a foul ball that hits Mio and he brings her a compress the next day. He notices that Mio always has a parasol and that he always sees her reading under the same tree in the courtyard. Their other classmates call Mio "shadowless" because of the parasol and the fact that she does not have much presence. Riki wants to help her like Kyousuke and the others helped him, so he asks Mio if she would like to join the Little Busters, but she declines. Later, Yuiko enlists the help of Riki to help find Mio's book. They go back to the classroom, but are unable to find it, thinking that someone may have hidden it as a joke. However, Yuiko arrives to explain that there was no wrongdoing, and the girl who had picked up the book before gives it back to Mio. Some of the Little Busters members come to get Riki for practice and Mio goes to watch them play.
野球の練習中、ボールを探していた理樹は物静かな少女・美魚と出会う。
いつも中庭の木陰で日傘を差し、ひとりで読書をしている彼女が何となく気になる理樹。
時に辛らつな彼女の言動に最初はとまどうものの、昼食をもらったりしてしだいに打ち解けていく。
美魚はある一冊の本を大事そうに読んでいたが、どんな本なのか聞いても教えてはくれなかった。
ところが体育の授業の時にその本をなくしてしまい、理樹がいっしょに探してあげることに。
항상 나무 밑에서 홀로 책을 읽고 있는 소녀, 니시노조 미오.
그녀는 학급 내에서도 존재감 제로로 불리우며 고립되고 있었다.
연습 도중의 실수로 우연히 미오와 인연을 맺게 된 리키는 그녀를 리틀 버스터즈에 받아들이기로 결심하는데...
练习棒球时，为寻找打飞的球的理树在树下碰见了安静的少女，美鱼。经常在树下一个人撑着阳伞读书的美鱼也引起了理树的注意。虽然一开始被美鱼刻薄的话语而困扰，但最后还是与她一起享用了午餐。体育课时，对美鱼而言十分重要的书丢失了，理树和她一起寻找这本书……
