Airi no Yu-u-wa-ku

After sending my sister in law to her field trip, I find Airi, my sister in law's classmate, standing next to me. Airi was unable to go to the field trip because of fever, and I somehow happened to live with Airi. I am an emergency teacher as well as Airi's teacher. I can't make any mistake to keep my face up for my lovely sisters in law. However, giving private lesson to her and living together with her... can I hold my desire from Airi's seduction any longer?