This ambitious work on the theme of darkness and light is a collection of six linked stories that treat impulsive killings, children's loss of parents to accident or illness, and other dark events of life while contrasting them with the bright light that also shines into the characters' lives. Kobai (literally "photophilous") is a word the author coined by analogy with entomophilous flowers, which are pollinated by insects, and anemophilous flowers, which are pollinated by the wind; it expresses the possibility that light might serve a similar function in making people's lives bear fruit?an idea that underpins the entire collection.
Each of the protagonists carries a very negative burden of some kind in his or her life. In the first story, we meet a man in his mid-forties who killed his father's lover when he was in high school and drove his father to suicide. He now runs the family shop he has inherited, but remains single and spends his time caring for an elderly mother who suffers from dementia. The second tale centers on a ten-year-old boy and his eight-year-old sister who frequent the riverbed to catch insects. Convinced that a homeless man has molested his little sister, the boy drops a large rock from the bridge onto the man's makeshift hut and believes he has killed him. The true killer of the derelict, however, is the protagonist of the third story. This man had a girlfriend named Sachi when he was in middle school. Her mother's lover was raping her, so she killed him. The fourth story centers on Sachi after she has grown into adulthood . . .