Arrow feathers
矢絣 yagasuri

An arrow flies straight and never comes back, so the pattern stands for determination. Brides received it as a wish not to return to their parents' home, and it is now the classic pattern for graduation hakama.
Edo period; schoolgirl fashion in the Meiji–Taishō periods
Arrow-fletching shapes were originally woven as kasuri (ikat) and later stencil-printed. Arrows belong to warrior culture, and in the Edo period a yagasuri kimono was given to brides as a charm, since a shot arrow does not return. From the late Meiji and Taishō periods it became the signature kimono of female students, worn with maroon hakama.
A 1970s manga, Haikara-san ga Tōru, revived the Taishō schoolgirl look, and yagasuri with hakama is now standard for women's university graduation.