Mina, Rui, Hajime, and Tokio, a close-knit group of young colleagues at a publishing company. Mina, bright and optimistic with a proactive approach to sex, and Rui, serious and reserved but secretly passionate. As they navigate their feelings for each other, a magazine's "Casual Sex Special" sparks a major shift in their dynamics. Is love a prerequisite for sex... or is it something else entirely? The conclusion they reach, whether brilliant or misguided, will shake the very core of their hearts.