Miyuki Hiiragi, an adult woman and mother to Yui Hiiragi, accompanies her daughter to an old observatory on Yui's twentieth birthday. Braving snowy conditions, this journey revisits a location they frequented annually during Yui's childhood. Miyuki's presence during the snowy trek triggers Yui's recollection of childhood memories, particularly those entwined with Miyuki and Yui's late father.