Shun is a transfer student who can't seem to adjust to his new class and falls into mild depression. However, one day he meets some fellow students by chance in front of a creepy Western-style mansion called the "Jailhouse" which is rumored to be home to a hideous blue monster. Soon, the group of six students, led by Shun and Anna, become trapped inside and desperately attempt to escape before the monster finds them.
Tadaomy Ando became a yakuza boss at a young age. Because of his subordinate, he quit the yakuza. Now, he learns from Takashi Konaka the trade of illegal money lending and how to collect debts. Tadaomy Ando decides to become a loan shark. He has customers, but has a hard time collecting debts.
Tukasa works for Tadaomy’s loan shark company. He picks up more female debtors because of his appealing looks. One day, Erina appears in front of Tukasa. Erina used to be an idol and she now sings on the street.
