The story unfolds as an 18-year-old Japanese girl, Erina, and her big-breasted friend, Yuki, prepare for a cosplay event. As they get ready, they can't help but feel attracted to each other. Their bodies brush against each other as they try on outfits and accessories. Their budding desires escalate when they catch sight of themselves in the mirror.
Yuki takes the initiative and kisses Erina passionately, pushing her away when she tries to pull back. Overwhelmed and confused by these new feelings, Erina retreats to the bathroom. Meanwhile, Yuki confesses her attraction towards Erina to a third-party character named Tomoki, revealed through the use of onscreen text messages.
Despite being hesitant, Erina eventually returns to find Yuki sitting alone. They confess their feelings for each other and decide to start a new chapter in their relationship.
