Milk manifests as one of three food spirits appearing after Mari consumes her least favored foods. Alongside Ninninman and Piiman, Milk becomes visible to Mari in the nurse's office following her fainting incident at school, a direct result of her ingesting milk, carrots, and peppers. Representing dairy specifically, Milk accompanies Mari alongside the other spirits. Together, they engage in activities designed to help Mari confront personal challenges, facilitating her journey toward overcoming fears. Milk operates strictly within the trio dynamic, with no individual actions, dialogue, distinct personality traits, backstory, or independent development described separately from this collective role supporting Mari's growth.