- WHAT IS JUKUSUI? JUKUSUI is a Japanese word that means “deep sleep” or “profound sleep.” We will support to get good sleep for people all over the world through our app from Japan. 【about JUKUSUI APP】 JUKUSUI is a multi-functional alarm clock designed to support and improve your sleep. ◆Lull Sounds The healing lull sound will be played to induce peaceful sleep. ◆Smart Alarm It detects your light sleep and wakes you up. We recommend this for those who always wake up feeling tired, who turn o