Yuma Okazaki and Hotaru Mizushina, longtime friends in high school, enjoy blissful lives with their boyfriends, Takeda and Fujiwara. Their unbreakable bond is evident through shared school activities and group outings. Yet, a pivotal moment unfolds during a group date when Hotaru surprises Yuma by stroking her thighs in a daring move. Startled, Yuma retreats to the restroom, only to be followed by Hotaru. Alone in a locked cubicle, Hotaru coerces Yuma, whispering, 'Practice with me to ease your nerves around boys.'