At the film's outset, the protagonist, Iguchi Seibei, faces the profound sorrow of becoming a widower after his beloved wife succumbs to tuberculosis. Her funeral is lavish, surpassing what a lowly samurai like Seibei could ever afford. He dedicates his days to working at a grain warehouse, diligently managing the inventory for his samurai clan. His peers, however, mockingly refer to him as "Tasogare Seibei," or "Twilight Seibei," because he rushes home each evening to care for his increasingly senile mother and his two young daughters, Kayano and Ito, rather than indulging in the typical evening banter and luxuries with his fellow samurai.
Despite his noble lineage, Seibei neglects his own grooming and attire, prioritizing the welfare of his daughters and the medical needs of his mother over personal appearance or the cost of a monthly bath. This routine takes a turn when Tomoe, an old childhood friend and sister of his compassionate colleague Iinuma Michinojo, returns to town after escaping an abusive marriage with Koda, a samurai captain. Tomoe develops a close bond with Seibei's daughters, bringing a momentary respite to their troubled lives. However, the peace is shattered when Koda intrudes on Michinojo's home one drunken night, demanding to see Tomoe. Seibei, determined to protect her, challenges Koda to a duel, despite the dire consequences of such an act within their clan.
Against all odds and facing the possibility of death, Seibei bravely faces Koda with only a wooden stick while the captain wields a steel katana. In an unexpected turn, Seibei triumphs, managing to spare both their lives. Following this encounter, when Iinuma offers Seibei a chance to marry his sister, it presents a deep conflict for Seibei. He feels improperly positioned to accept, believing his lower status would burden Tomoe with poverty as he struggles to care for his daughters and mother. This leads to a silent sorrow as Tomoe gradually distances herself from Kayano and Ito.
As the narrative unfolds, Seibei is summoned by the head of his clan, who, having heard of his exceptional skills with a sword, commands him to eliminate a Yogo Zen'emon, a disowned samurai reluctant to commit seppuku. With the clan's leadership in turmoil following the death of the young lord from measles, Seibei feels an overwhelming reluctance to accept this deadly mission, requesting two days to gather his thoughts. However, the new clan leader grows impatient and expels him from the clan, prompting Seibei to reconsider.
Ultimately, he resolves to take on the mission. As he prepares for what could very well be his last fight, he seeks Tomoe's aid in completing the necessary rituals for a samurai about to face battle. Before leaving, he confesses he regretted not proposing to her earlier and wishes to ask for her hand in marriage now that a promotion is at stake. Heartbreakingly, Tomoe reveals she has already accepted another proposal, causing Seibei to feel foolish for even suggesting it. They part ways, emotionally charged yet understanding the twist of fate that separates them.
In a tense encounter at Yogo's residence, Seibei finds his target in a grim setting. Yogo, recognizing Seibei, offers him a drink and pleads for an escape, recounting his own losses to tuberculosis and the debt of gratitude he owes to his former master for a proper burial. Seibei, relating to Yogo's plight, opens up about selling his katana for his wife’s funeral, showcasing his own sorrow. Tension escalates, leading to a fierce duel where Seibei's unique fighting style is pitted against Yogo's superior swordsmanship. Ultimately, despite his injuries, Seibei emerges victorious but limps back home to a joyous reunion with Kayano and Ito, alongside Tomoe, who has remained steadfastly by his side.
The epilogue reveals a bittersweet fate: Seibei's life comes to an end in the Boshin War three years later, leaving behind a legacy intertwined with hardship. His daughter Ito points out that while others may regard her father as a tragic figure full of misfortune, she sees him differently. Her father, devoid of ambitions for greatness, found solace in his love for his daughters and the affection of the beautiful Tomoe.
