Ha Gyeong's first love, Do Ha, reappears in the midst of summer. A property sale goes awry, and old wounds reopen as their summer ignites once more.

Back from a 2-year hiatus, Do Ha refuses defeat and attempts to win back Ha Gyeong's heart. Old memories from a summer past unlock as the rain pours.

The Patan High School Project reunites the two. Under the Summer Triangle, first love emerges once more as Do Ha reveals his heart to Ha Gyeong.

After attempting to quit the project, Do-ha confronts Ha-gyeong about leaving the Peanut House. Later, the two team up to seek local leaders' approval.

Ha-gyeong and Do-ha settle into a new living situation and continue working on the Patan High project. But their mutual rival Nam-jin causes trouble.

Memories resurface as a shooting star lights the sky. Past and present collide as a confession is evaded. The name Baek Do-yeong casts a long shadow.

Do-ha's resentment over Ha-gyeong's new relationship grows. Seul becomes concerned after Seung-taek experiences pain during his hockey match.

Do-ha takes a confused Ha-gyeong out for the day. But while struggling to express her feelings, her drinking leads to a series of embarrassing errors.

Secrets unfold as Ha-gyeong breaks up with Su-hyeok and finds herself entangled with Do-ha. A double date at an amusement park deepens their rapport.

Do-ha’s long-kept secret, Baek Do-yeong makes a comeback. Tears override laughter at the Peanut House, and the residents are at another crossroads

Even if the peanut house collapses, the hearts of two people must be rebuilt. Unspoken truths, confessions of love spilling out like sleep talk. The moment when the true betrayer surrounding the solar power project is revealed. Two people standing together in the fight to protect their neighbors and village. "What will the model we will create in the future look like?"

In the final summer, the two finally become true lovers. In a world where every day felt like war, they now promise to protect each other. They spend birthdays, anniversaries, and even the smallest moments together. Their love, sometimes cheerfully, sometimes seriously, continues. "Summer is over, but our story is just beginning."