Primary school student Keita Amano possesses a curiosity as innocent as that of any other child his age. However, when he decides to venture deeper into the forest one day, he encounters a small, mysterious capsule. From its depths emerges Whisper. After 190 years of imprisonment, this ghost-like creature is grateful that someone was kind enough to set him free. He decides to reward Keita by becoming his guardian against supernatural forces. Whisper is one of many Youkai that exist in the world, and he provides Keita with a special Youkai Watch, which enables him to see and interact with all the other Youkai. Youkai Watch follows Keita, Whisper, and the cat spirit Jibanyan as they encounter Youkai, befriend them, and fix the trouble they so often cause. With the help of the watch, they use the powers of previously encountered Youkai to aid them. Young Keita may have been just an ordinary primary school student when he first encountered the Youkai, but the many adventures that follow his discovery provide him with invaluable experiences and precious life lessons that help him grow.