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 Happy Land 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!

You lead quite a nice life... Competing with your friends... Having a childhood-almost-girlfriend, who is coming back to town... All dreams starting to come true... when the ground suddenly shakes and a shelf drops on your head.... Well... You hit your head just now, so it'd be quite... reasonable that everything went nuts and people get eaten before your eyes, wouldn't it?