My wife Yui is pure and beautiful, the most important person who protects our home. One day, a man named Isobe, her former homeroom teacher, suddenly showed up at our house. I felt uncomfortable with his attitude and quickly sent him away. But a few days later, I discovered Isobe's smartphone wedged in the gap of the sofa. I was certain I had cleaned this area yesterday—how could it have been left here? How long had it been there, and what was his true purpose for coming? Overcome by growing anxiety and suspicion, I couldn't help but peek into the contents of his phone...