Blue Demon by Daisuke Kobayashi

4.50

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.