Episode 9 of "Cinderella at 2am" commences with a spark reigniting between Yoon-seo and Ju-won as they cautiously rebuild their connection. As Ju-won escorts Yoon-seo to her doorstep, he slyly slips inside, stealing a moment of intimacy with a tender kiss. However, the fleeting embrace is cut short as Yoon-seo insists on his departure, mindful of Ji-suk's imminent return. Amidst the lingering passion, Ju-won beseeches Yoon-seo for a definitive answer to his heartfelt proposal.
Yoon-seo, later in her room, engages in a lively brainstorming session with I-rae, concocting grandiose yet impractical plans to accept Ju-won's offer. Each idea surpasses the realm of the ordinary, ultimately leading to nothing but laughter and frustration. Upon returning home, Yoon-seo finds Ji-suk divulging his aspiration to attend culinary school, prompting her to present him with a bankbook filled with her meticulously saved funds, a testament to her unwavering support.
Determined to respond to Ju-won's affections with a clear conscience, Yoon-seo visits the chairwoman, returning the financial gift she had received. Yet, the chairwoman remains steadfast in her opposition to their union. The aftermath sees Yoon-seo relieved of her duties, a likely consequence of the chairwoman's disapproval, stirring up Ju-won's indignation. Nevertheless, Yoon-seo's soothing words quell his anger, painting a picture of resilience amidst adversity.
Seizing the opportunity of Yoon-seo's newfound freedom, Seong-min invites her to his studio, celebrating her liberation from work. However, their joy is inadvertently interrupted when Ju-won overhears the invitation during a phone call and promptly joins them. A dinner celebration ensues, during which Yoon-seo briefly steps away to visit Ji-suk's nascent culinary school. In her absence, Seong-min and Ju-won, under the influence of alcohol, forge an unlikely bond, with Seong-min confessing his own admiration for Yoon-seo, to Ju-won's surprise.
Elsewhere, Si-won and Mi-jin share a dinner laced with subtle undercurrents of jealousy. Si-won's mention of a past love prompts Mi-jin to retaliate with a similar revelation, leading to a childish spat fueled by envy. However, the following day brings a heartening turn as Si-won clarifies his feelings for Mi-jin, apologizing for his previous behavior. Mi-jin reciprocates with equal honesty, confessing her own affection, and their relationship blossoms into a romantic embrace.
Meanwhile, Ju-won, still under the sway of alcohol, finds himself at his mother's doorstep instead of his intended hotel. Inspired by Seong-min's words, he pours out his heart to his mother, voicing his earnest desire for happiness. The next morning, his mother, in her subtle way, conveys her tacit approval for their union, leaving Ju-won overjoyed. He promptly shares this development with Yoon-seo, who later collects him from work, embarking on a day trip to a serene campsite. There, amidst the tranquility of nature, Yoon-seo accepts Ju-won's proposal, slipping on the ring he had offered her, sealing their love with a promise for eternity.
