The series follows the burgeoning sexual relationship between the shy yet curious Yui and her childhood friend, the increasingly bold Kyouichi. Their lives take a lewd turn when they discover the 'Mutual Love Note,' a magical notebook that forces them to act out any sexual desire written within its pages. The story begins with innocent hand-holding and quickly escalates into intense, passionate encounters. Kyouichi, driven by his long-held lust for Yui, uses the notebook to explore every inch of her body. Viewers witness their first kiss evolve into deep, wet French kissing, his fingers exploring her drenched, dripping slit until she's begging for more. The animation graphically details scenes of him mercilessly fucking her tight, wet pussy in various positions, from a passionate missionary to a deep, pounding doggy style that makes her tits bounce. Her moans of pleasure fill the air as she cums multiple times from his relentless cock. The series highlights their mutual exploration of lust, including intense oral sex where Yui deep-throats his throbbing shaft and he licks her clit to explosive orgasms. Each episode unveils a new fantasy, culminating in a raw, creampie-filled finale where their bodies are slick with sweat and cum, forever bound by the notebook's sexual power.