My brother and sister-in-law suddenly had to go overseas for work, so I ended up looking after my niece, Yui, while they were gone. One day, while I was reading a classic literature book, Yui seemed to have become interested in the story of forbidden love in it. From then on, she started tempting me, calling it "forbidden love." Her provocative displays and close proximity shattered my rationality, and I became prey to my little devilish niece's schemes!