Sai is the name of the female character in Seizo Watase's romantic manga which bears her name. In English "Sai" translates into beautiful young heroine.

The manga tells the tale of a married couple who live in modern day Japan. This series is meant for adults... not that it is X rated or contains subject matter unfit for children, quite to the contrary. Sai is simply the story of an adult couple's love for one another.

The backdrop for the tender narratives is everyday life in the big city, but the eternal love affair between the married couple is always the focus of the stories.