It all begins when 6 young boys start a new school year, unsure of how to find their place. Each tries to adapt in their own way, but even the simplest things, like approaching someone or starting a conversation, can feel complicated.
The notebook represents those little thoughts that try to guide them when they don't know what to do. However, little by little, those plans stop working, and everything ends in an unexpected accident. What seemed like a chaotic moment becomes the first step in their paths crossing.

The school accident brings them together. Something that began as an unexpected moment becomes the reason why six very different people begin to forge a shared history.
However, before forming that connection, each faces their own insecurities. Shinyu seeks refuge in rap, but tends to remain in his own world. Jihoon tries to distance himself from what he loves because he fears not fitting in, while learning that accepting who he is also means accepting his tastes. Hanjin arrives in a completely different environment, with the uncertainty of someone starting from scratch and unsure if he will find his place. While some already had a prior connection, like Dohoon, Shinyu, and Youngjae, others arrive later, like Hanjin, Jihoon, and Kyungmin.

Over time, this friendship becomes a vital support for each of them. Shinyu faces his own doubts during competitions, but discovers that he doesn't have to overcome everything alone.
The idea behind "S" and "N" represents how different people can complement each other. While one struggles, the others help him move forward, demonstrating that their differences are precisely what makes the group strong.

After sharing so many moments at school, the boys seek to create memories outside of it. During the summer, they find a place they feel is their own, a space where they can enjoy themselves without worrying about the passage of time.
The marks on their hands serve as a map of everything they experienced together. Each place and each moment is etched as proof that their stories are already intertwined. The final constellation represents that, although each has their own personality, they are part of the same whole.

But after summer comes winter, and with it, the end of a chapter that shaped their lives. Graduation brings with it memories, regrets, and feelings that were never spoken aloud.
Love emerges as a representation of everything they wanted to express before moving on. Shinyu, Dohoon, and Hanjin experience different ways of loving someone: one with admiration, another with a more direct and confident connection, and another with a sense of distance.
Meanwhile, Youngjae, Jihoon, and Kyungmin grapple with their own feelings. Kyungmin feels he never had a chance, Youngjae decides to distance himself despite his feelings, and Jihoon values their friendship more than anything else.
In the end, not all feelings have to blossom into a love story; some simply become part of the memories they carry with them.

After leaving school, a completely new chapter begins. The freedom to grow up comes with new responsibilities, decisions, and experiences that once seemed distant.
Now they no longer have the same guidance as before, but they begin to discover who they are and what path they want to follow.

University becomes the next chapter in their lives. Although they're entering a different world, they still carry the memories of where it all began.
Unexpected encounters remind them that some connections remain even as time passes. It's like meeting someone for the first time, but with the feeling that there's already a history behind them.

Adulthood begins to feel more intense. Now they must face the world differently, seeking independence and demonstrating that they can move forward on their own.
It's a stage where they discover their strength and feel they can achieve anything, even if the path is more challenging.

Over time, each of them begins to build their own life. Some seek new experiences, others focus on their goals, and still others find new ways to express themselves.
Even though they're no longer always together, each path still carries a part of what they experienced as a group.

Young adulthood arrives with more intense emotions. Romance, new experiences, and freedom make everything feel stronger than before.
It's a stage where happiness and uncertainty coexist, yet life continues to move forward.

So many stages of searching for guidance, they now learn to trust their feelings. Love ceases to be something they need to fully understand and becomes something they simply experience.
The person they love represents security, happiness, and an emotion difficult to explain. They no longer need to have all the plans laid out like they did at the beginning, because now their own feelings are what propel them toward new possibilities.