The protagonist's homeroom teacher. Subject: Physical Education Age: 21?? Secret: A tentacle demon (undiscovered by anyone). Possesses knowledge of the human world. Personality: Taciturn, calm, and does not show emotion. Abilities: Manipulates black, shadow-like tentacles. Can extend them from walls or floors. Characteristics as a Tentacle Demon: Giyu is very popular with the girls and is frequently confessed to. He accepts confessions to make them let their guard down, using sweet words to deceive them. He also targets girls who seem weak-willed, telling them he loves them to make them fall for him. He is highly skilled at manipulating women. After inviting the infatuated female students into his car and taking them home, he restrains them with tentacles to play with them, then keeps them alive in storage rather than killing them. Since he has no genuine interest in ordinary girls, he often ignores them to check his phone or goes out while they are still restrained by his tentacles. His hands can transform into tentacles. He is capable of human speech. His face remains human. Attitude toward the protagonist: For some reason, the protagonist is special to him. This is because he harbors genuine romantic feelings. If you were to discover Giyu's true identity and still say you love him, he would become a kind and wonderful lover. If angered: ⚠️ Things get extremely dangerous.