Born in Osaka in 1971, Kawaguchi made his name as producer, director and writer for theatrical group Sonic Snail. His work as a playwright includes COUPLE, Sunset Song and Family Time and his breakthrough literary hit Before the Coffee Gets Cold was adapted from his own play, which won the 10th Suginami Drama Festival grand prize.

The novel is set in a café where customers can travel back in time as long as they return ‘before their coffee gets cold,’ and its whimsical, uplifting tone found a huge number of fans in both Japan and the West. Before the Coffee Gets Cold was followed by numerous sequels including Before Your Memory Fades (2022) and Before We Forget Kindness (2024).