the rumor of the locked boys’ bathroom at school. Students believe something strange or supernatural is happening there because the door is always locked and no one seems to know why. Kanna becomes curious about the rumor and looks into it, which leads to a connection with Shiraishi-sensei. With Chuzenji-sensei’s help, the mystery starts to make more sense as he explains the real reason behind the situation, showing that the scary rumor has a more logical explanation.