As the taxi rides silently, Sang-hak, Eun-jung, and Sang-yeon make their way back to rejoin the others in Episode 5 of "You and Everything Else." In private, Eun-jung confesses a burdened heart, weighing the guilt of witnessing Ms. Yoon's state and Sang-yeon's motive to bring them there, which she feels was solely to inflict hurt. Sang-hak boldly inquires about Sang-yeon's brother's demise, revealing a shocking truth—he committed suicide. Eun-jung bears the weight of this tragedy, convinced that her inaction, specifically not giving him the clover or making more of an effort to intervene, played a part in his death. This honesty forges a deeper bond between them but also stirs up issues for Sang-yeon. She becomes cold and distant, shunning her mother's calls, a delicate situation considering her impending move-in with Eun-jung.
Sang-yeon's affection for Sang-hak is evident, not least in the photo of him in her book, fueling her jealousy over his blossoming relationship with Eun-jung. This jealousy escalates when she learns of their upcoming trip to Gapyeong together. During their stay, Sang-hak makes a wish with Eun-jung, dreaming of returning to this place upon his military discharge. As they lie together in bed, he confesses his deep affection for her.
Sang-hak eventually enlists with the other men, giving Sang-yeon a knowing glance before departing—a glance filled with unspoken words and emotions. Three months later, at the house, Sang-hak sends a letter to Eun-jung. Before she can open it, Ms. Yoon's ringing attempt intrudes, creating an awkward moment as Sang-yeon enters, leading to a confrontation between the two.
Sang-yeon scoffs at the notion of mending fences with her mother, dismissing Eun-jung's concerns about their strained relationship. The aftermath of this altercation sees the pair go days without a word, each consumed by their own thoughts. Eun-jung channels her energy into developing Sang-hak's photographs, presenting them to Sang-yeon in an envelope, a precious window into the past. The images evoke a flood of memories, and Sang-yeon struggles to hold back her tears. Eun-jung hears her crying from across the table, admitting she had no idea how deeply this would affect her.
Sang-yeon takes the photographs to her mother, revealing a glimpse into their tumultuous past. It emerges that Sang-yeon showed Sang-hak's diary to her mother out of curiosity, only for her mother to turn on Sang-yeon and blame her for the ensuing conflict. Witnessing her mother and father fighting over Sang-hak's love life entries, Sang-yeon blames herself for the pain it caused.
Despite this, Sang-yeon is determined to find closure and sets out to track down the woman her brother was corresponding with. She speaks to Sang-hak, confessing his death - a fact he already knew, given Eun-jung's revelation - and they take a stroll together. Eun-jung's unexpected appearance at the subway station interrupts their time, leaving Sang-yeon feeling like a third wheel and walking away from the pair.
The narrative then flashes back to 1998, where we see Sang-yeon slipping into a deep depression after moving in with her mother. With her brother gone and her father absent, her mother's cold and distant behavior only exacerbates her suffering. Sang-yeon finds herself researching 4-digit codes and eventually hacks into her brother's PC. When she opens the chatroom, she finds an incoming message from Kim Sang-hak, who admires his brother's work and even defends him against his friends' taunts about his absence from a diner. Sang-yeon listens in on these exchanges, feeling a sense of connection with her brother even in death.
Sang-yeon maintains the ruse about her brother's continued existence, feigning his presence in online conversations with the photography group, as she is painfully aware that these individuals are ignorant of the truth. Our Sang-hak, operating under the alias of Uncle Tat, engages in a separate chat with Sang-yeon, unaware that he is not communicating with Cheon Sang-hak but rather his sister. This charade continues for a while, until time passes and Sang-hak goes silent for an extended period. Eventually, he messages the group, encouraging them to showcase their work at a gallery. It is during this moment that Sang-yeon captures a picture of him admiring the artwork.
Just before Sang-hak approaches her, he is halted by his friends' attention-seeking antics. Sang-yeon decides against intervening, and as a result, when she later joins the photography group and discovers that Eun-jung and Sang-hak are dating, she feels her heart shatter into a million pieces.
In the present, Sang-yeon and Sang-hak take a stroll up into the mountains together. Sang-hak admits to understanding a little of what she is going through and mentions their online friendship. The truth is, Sang-yeon is struggling to keep her true feelings at bay, as she is clearly head over heels in love with him.
When Eun-jung showcases the photos from Sang-hak's latest reel, Kim Sang-hak recognizes his brother and the woman he once admired. Sang-hak confronts Sang-yeon and realizes that she is the one who replied online on behalf of her brother, her secret finally revealed.
