The story centers on Kim Min-ji and Kang Yu-na, two best friends who have been inseparable since childhood. Their relationship is built on a foundation of deep trust and shared history. However, as they transition into young adulthood, the nature of their bond begins to shift. What was once comfortable and platonic becomes charged with a new, confusing tension. This shift is catalyzed by a series of "bad thoughts" — intrusive, erotic, and emotionally heavy fantasies that Min-ji begins to have about Yu-na.
At first glance, the name sounds counterintuitive. Why would anyone want to document their darkest, most irrational thoughts? Isn't that just wallowing in misery? Surprisingly, psychologists and cognitive behavioral therapists argue that a dedicated "Bad Thinking Diary" is one of the most effective tools for breaking the cycle of rumination. It is not a diary of self-pity; it is a diary of self-defense. Bad Thinking Diary
Anxiety feels random. It attacks without warning. But a diary reveals the pattern. You might realize that your bad thinking only spikes on Sunday nights (work anxiety) or after you haven't eaten for five hours (blood sugar crashes). The diary provides data. And data defeats the mystery of fear. The story centers on Kim Min-ji and Kang
With Elena unemployed and depressed, she becomes clingy, leaning on Maya harder than ever. Maya feels trapped again. The "good girl" instinct wants to help, but the "diary brain" wants her gone. Simon returns to work early, bitter and vindictive. He targets Maya for a harsh performance review. Maya writes a new entry, fueled by wine and rage: “I hate them. I hate how they drain me. I wish they would just disappear. I wish they were gone forever.” What was once comfortable and platonic becomes charged