The anticipation for Kitty's 18th birthday is palpable as the episode begins. Her father, eager to celebrate, hands her a hefty envelope of cash. She shares her excitement with Yuri about their shared connections with Min Ho and Juliana. However, as the day unfolds, a few notable events occur before her actual birthday party.
Kitty notices that Yuri has not responded to her party invitation, and when she confronts Yuri about it, she gives a flimsy excuse that upsets her. As the day progresses, more of her friends give similar excuses for not attending. Kitty senses something amiss and confronts Q, who reveals that everyone is secretly planning a surprise party and asks her to pretend not to know about it.
At school, Kitty learns that Min Ho is leaving for LA to visit his mother, which means he will miss her birthday. Min Ho also tells Marius that he's hesitant to confess his feelings because Kitty has chosen NYU.
Elsewhere, Kitty shares her decision to attend NYU with Professor Lee. Alex overhears part of the conversation and later informs his biological father about Jiwon's pregnancy and his desire to be involved. Professor Lee is surprised but understanding and supports Alex's decision. Alex asks him to be a part of the child's life as well.
Eunice sends a desperate message to Min Ho, asking him to meet. She informs him that a girl group wants him as their manager after seeing his work with her. Eunice and Dae encourage Min Ho to consider the opportunity despite his father's disapproval. Dae also shares that he wants to inform his father about leaving engineering.
Q invites Jin to be his date to Kitty's birthday party. Meanwhile, Kitty celebrates early with Alex and Jiwon. She encourages them to tell Jiwon's grandmother about the pregnancy. Later, she brings Halmoni to meet Alex. Jiwon explains her decision to live life on her own terms, and Kitty supports Alex in Korean, which impresses Halmoni. She accepts both of them with open arms.
What transpires at Kitty's surprise party? As the night unfolds, Kitty embarks on a journey of pretense, ready to play the part of the surprised guest. Lara Jean's call brings delightful news – her novel is about to be published, adding to Kitty's joy at the reunion of Lara Jean and Peter. Soon thereafter, Q leads Kitty to the party venue, where she's met with a flurry of surprises from her friends. Among these, Min Ho's presence is particularly startling. He presents her with her mother's cherished flowers, a touchstone of their shared past. Yuri, in turn, gifts Kitty the dress she'd coveted and reveals her own aspirations to start a fashion line.
Emotional and grateful, Kitty opens her gifts, thanking her friends for their thoughtfulness. Meanwhile, Q confides in Jin about arranging an interview, only to be met with a resolute refusal. Respecting Jin's decision, they both reveal their mutual feelings for one another. Elsewhere, Yuri and Juliana engage in a heart-to-heart, leading to their reconciliation.
Does Kitty and Min Ho's story reach a harmonious conclusion? As couples begin to dance, Kitty stands alone until Min Ho extends an invitation. During their dance, Min Ho shares that he's canceled his trip to LA to be with her. He inquires about her decision regarding NYU, to which Kitty replies that it was made solely for herself. Min Ho admits his uncertainty about his future, leaving the moment open-ended.
Does Min Ho deter Kitty from her journey to Portland? The following day, as Kitty prepares to depart for winter break in Portland, she inadvertently leaves her diary behind. Meanwhile, Min Ho and Dae discuss their shared love for music, reflecting on Kitty's unwavering support. Realizing his feelings, Min Ho rushes to catch up with her but learns she's already on her way to the airport. Yuri and Juliana suggest he take the subway. Min Ho sends Kitty a song expressing his emotions. He misses her train but decides to meet her at the next station.
How does "XO, Kitty" Season 3 conclude? On the train, Kitty listens to the song, reminiscing about their shared experiences. At the next stop, Min Ho meets her and confesses his love. Kitty reciprocates, telling him she feels the same way. The season ends with Min Ho joining Kitty on her flight to Portland for winter break – a new chapter in their budding romance.
