"One Week Friends" centers on the relationship between high school students Kaori Fujimiya and Yuuki Hase. Kaori suffers from a unique condition where her memories of friends reset every Monday, erasing any recollection of the bonds she formed during the week. Despite this, Yuuki, a classmate, becomes determined to befriend her, even if it means reintroducing himself each week. The narrative explores their evolving connection as Yuuki persistently reaches out to Kaori, offering her kindness and understanding despite the challenges posed by her memory loss.

The story delves into themes of friendship, perseverance, and the fragility of memory. Kaori’s condition creates a poignant dynamic, as she struggles with the fear of losing her connections while Yuuki remains steadfast in his efforts to support her. Over time, their relationship deepens, and Kaori begins to trust Yuuki more, even as she grapples with the emotional toll of her condition. The manga also introduces supporting characters, such as Shougo Kiryuu and Saki Yamagishi, who contribute to the story’s exploration of friendship and the ways people navigate personal struggles.

As the narrative progresses, Kaori’s condition becomes a focal point for examining the resilience of human connections. The story balances moments of warmth and humor with a sense of melancholy, creating a heartfelt portrayal of the challenges and rewards of forming meaningful relationships. Through its focus on Kaori and Yuuki’s bond, "One Week Friends" offers a thoughtful exploration of how people cope with adversity and the enduring power of friendship.