Welcome to Happyland, an extreme amusement park! The Komiya family is not unusual is any way, two parents love each other and their two children, who are healthy, happy, and accomplished at school and with extracurriculars. In appearance, they're an ideal family that has everything going for them!

At least… That's what they believed until the father decided to take them to spend a day at Happyland Park. In this park with its extreme attractions, the most shameful secrets will emerge in the most literally explosive way possible! A horrifying and gory tale of survival begins in this first of two volumes by Shingo Honda!