When Keita Amano, a curious primary school student, stumbles upon a mysterious capsule in the forest, he releases Whisper, a friendly ghost-like Youkai trapped for 190 years. Grateful for his freedom, Whisper becomes Keita's protector against supernatural threats. Equipped with a special Youkai Watch, Keita can now see and engage with other Youkai. Alongside Whisper and Jibanyan, a cat spirit, Keita embarks on adventures to befriend Youkai, resolve their mischief, and harness their powers. Through these escapades, Keita undergoes personal growth, learning valuable lessons that shape his character.