On the final day of summer vacation, Kokona Aoba is ready to spend some long-awaited time with her mother, but these plans are unfortunately canceled due to work. Opting to go outside instead, she takes a stroll down a familiar path—one where fond memories appear at every corner. 
 
Later, in the middle of autumn, Hinata Kuraue and Aoi Yukimura are looking through a scrapbook of their childhood. Snooping around in Aoi's room, Hinata finds that she has kept a strange acorn as a keepsake, but doesn't remember the reason why. As its discovery dwells on her, a wave of old memories comes forth, causing her to reminisce about a forgotten event from her childhood. 
 
From time spent with loved ones to promises from the past, Yama no Susume: Omoide Present follows the three girls as they cherish old memories while crafting entirely new ones to remember.. 
 
(Source: MAL Rewrite)