The film unfolds the tradition-minded world of "Kyozome", a dyeing handicraft maintained proudly for ages in Kyoto and well-known throughout Japan.
Undercurrent is a love story. The heroine is Kiwa, the daughter of the aged owner of a cloth-dyeing factory. The industry is moribund and the mainstay of the factory is Kiwa, who not only creates original new patterns, but also strives to promote her designs by exhibiting them in the city. One day at Toshodaiji temple, Kiwa meets a university professor who does research on the Scarlet fly. She finds herself losing her heart; she begins to dye materials in red and is chided by her father for acting like a real woman.
Kiwa wins a competition for Kimono design - her motif the Scarlet fly. She grows reckless, forms a liaison almost openly with the married Takemura. the professor.
The professor's wife dies; paying her respects, Kiwa recalls the passionate words uttered by Takemura shortly before, "Wait, just a little longer ..."
Disillusioned, she renounces her love - and as if symbolical of her feelings, the May Day parade is flying its red banner as she watches on.
The photographer of Undercurrent is Kazuo Miyagawa, who was responsible for Rashomon and the director, Kimisaburo Yoshi-mura. was recipient of Award at Venice for directing The Tale of Genji.