In the season finale of "Yuzuki-san Chi no Yonkyoudai," the youngest Yuzuki, Gakuto, begins a new chapter in his diary. His brothers encourage him to delve deeper into his thoughts and feelings, expanding the diary's scope beyond everyday events.

In a heartwarming scene at the Yuzuki household, Hayato, the eldest, comes home early to cook Gakuto's favorite mackerel with sake. This thoughtful gesture highlights his desire to strengthen family bonds. Amid these familial moments, Minato struggles with his studies, prompting Mikoto to step in as a tutor. Their interaction showcases the typical highs and lows of brotherhood. Gakuto's curiosity about Hayato's feelings as an older brother is also addressed. Hayato's response, appearing surprised and somewhat flustered, reveals his caring, almost grandfatherly attitude toward his younger siblings.

A pivotal moment in this episode is the family's monthly visit to their parents' grave. This solemn tradition, marked by respect and remembrance, adds deeper layers to the family's narrative, showcasing their enduring connection. After this reflective moment, the brothers spontaneously decide to extend their time together, leading to an impromptu picnic.

By the episode's end, Minato suggests keeping a shared diary with Gakuto, which evolves into a collective diary for all the brothers. This shared diary becomes a symbol of their unity and shared journey as the season draws to a heartfelt close.