In Episode 1 of "Jiisan Baasan Wakagaeru," Shouzou and Ine, an elderly couple reflecting on their life together, discover a golden apple on a tree. This tree was planted over sixty years ago to celebrate their wedding. The tree was once damaged by a typhoon but miraculously bore fruit. After eating the apple, both transform back into their youthful selves. Thrilled by their regained youth, Shouzou suggests finally going on their honeymoon.

Their granddaughter Mino visits them and is surprised by their transformation. Despite their youthful appearance, Shouzou insists on maintaining his new look, although Mino objects to him cutting his hair. The couple's transformation astonishes the locals, who had grown accustomed to seeing them in their old age.

Shouzou and Ine decide to stay in their hometown, even though their son Yoshiaki worries about their well-being. The community notices that Shouzou is still young and asks him to participate in the upcoming sports festival. They hope his youthful energy will lead the team to victory.

During the festival, Shouzou and Ine's participation revitalizes the team spirit of Minamimachi. This leads to unexpected wins in various events, including a dramatic victory in the three-legged race and basketball shooting.

The episode ends with Shouta presenting a gift to the Saitou family as a sign of respect and recognition for their achievements at the sports festival.