The Chirping of Angels

Sanae Kitajima is a psychiatrist specializing in end-of-life care. Her boyfriend, Takanashi, who once struggled with a deep fear of death, returns from an Amazon expedition profoundly changed. What happened during the expedition? What is the true meaning behind his cryptic words, "I can hear the whispers of angels"? (Source: Asahi Shimbun Shuppan, translated)