Teenage Sunny, a nonverbal shut-in (or hikikomori) dealing with the death of his older sister, leaves the house for the first time in years when his old friend Kel appears suddenly on his doorstep. At the same time, Sunny's dream-world alter ego Omori embarks on a quest with Kel and their friends Aubrey and Hero to search for Basil, a missing member of their group.

Together the party must navigate the perils of this strange world, as well as their complicated feelings and repressed memories, to move forward and find what they've lost...!