Tokyo, 1962. Shūhei Hirayama (Chishū Ryū), an elderly widower, navigates life with his grown children: his married son Kōichi (Keiji Sada), along with his two unmarried offspring, 24-year-old daughter Michiko (Shima Iwashita) and 21-year-old son Kazuo (Shin'ichirō Mikami). The children’s ages and their memories indicate that their mother passed away shortly before the war's conclusion, likely during the bombings of Tokyo between 1944 and 1945. Kōichi has established a new life with his wife in a modest apartment, leaving Shūhei and Kazuo in the care of Michiko.
Hirayama enjoys regular reunions at a restaurant named Wakamatsu ("Young Pine") with five of his former classmates, including Kawai (Nobuo Nakamura), Horie (Ryūji Kita), Sugai (Tsūzai Sugawara), Watanabe (Masao Oda), and Nakanishi. Together, they share laughter and reminisce about their younger days, with Horie often bearing the brunt of their jests regarding his new younger wife and whether he requires pills for his vitality.
One day, their former Chinese classics teacher, Sakuma (Eijirō Tōno), affectionately known as the Gourd, attends a reunion. Through a casual remark, it becomes clear that Hirayama had pursued a career as a naval officer post-school, remaining dedicated to his service until 1945. After some drinks, Sakuma, now down on his luck, is found running a modest noodle shop in a less affluent area. His daughter, Tomoko (Haruko Sugimura), missed her chance at marriage in her youth, leaving her too old to entertain such thoughts now.
Moved by their old teacher's plight, Sakuma's former students resolve to support him with a monetary gift. Hirayama returns to the noodle shop to deliver the aid, where he encounters Yoshitarō Sakamoto (Daisuke Katō), who recognizes him as the captain of his wartime ship. Sakamoto introduces Hirayama to his favorite bar, where the bar's owner, Kaoru (Kyōko Kishida), strikingly resembles Hirayama’s late wife. The atmosphere becomes lively when Kaoru plays Warship March, and Sakamoto humorously enacts a military drill, singing along to the tune, invoking memories of wartime propoganda.
Meanwhile, Kōichi borrows 50,000 yen from Shūhei, pretending it’s for a refrigerator, but intends to splurge on second-hand golf clubs instead. His wife, Akiko (Mariko Okada), firmly disapproves and threatens to spend similarly on an expensive handbag if he indulges. Eventually, she softens her stance.
The Gourd confesses to his students that the choice to keep his daughter home to care for him has resulted in her lonely spinsterhood. Grieved by this revelation, Hirayama confronts his own selfishness in keeping Michiko at home and decides to arrange a marriage for her. He tasks Kōichi with inquiring if Miura (Teruo Yoshida), whom Michiko adores, might be interested. Unfortunately, Miura is already engaged, much to Michiko's placid demeanor, but her younger brother, Kazuo, soon reveals her tears after the news breaks. Subsequently, Hirayama invites Michiko to meet a potential suitor, which she reluctantly accepts.
In one of Ozu's classic ellipses, Michiko is soon seen clad in a resplendent wedding kimono and head-dress, indicating her acquiescence to marriage; however, neither the groom nor the wedding ceremony is depicted. After the wedding, Hirayama joins friends at a bar whilst Kōichi, Akiko, and Kazuo await his return home. Eventually, when he staggers back, inebriated, Kōichi and Akiko leave, and Kazuo heads to his room, leaving Hirayama alone.
In the poignant final scene, a tipsy Hirayama sings bits of the Warship March, concluding with the reflective words, > "Alone, eh?"
