Isshuukan Friends (One Week Friends) follows Yuuki Hase, a sixteen-year-old who finally works up the courage to ask Kaori Fujimiya, the quiet girl he likes, to be friends. Kaori keeps to herself and answers almost everyone with a cold rejection, but Yuuki soon discovers that her distance is not simple shyness. He later finds her eating lunch on the roof, where she secludes herself during break, and begins meeting her every day in the hope of understanding her better.
As they spend more time together, Kaori slowly opens up to him, but by the end of the week she pulls away again. Yuuki then learns the truth behind her cold front: after an accident in middle school, Kaori loses her memories of everyone close to her, except her family, and her recollection resets every Monday. Once a popular and kind girl, she now avoids friendship because she fears hurting the people she cares about.
Refusing to accept that a bond has to disappear every seven days, Yuuki keeps asking the same question each Monday: "Would you like to be friends?" Isshuukan Friends becomes a gentle story about patience, trust, and the fragile effort required to build a connection that can survive repeated loss.