Yukko, the Ota family's golden longhaired dachshund, sports light cream fur on his chest, paws, and underbelly, along with a red collar and his breed's characteristically grumpy expression. He joined the household before Kun's birth and initially commanded full attention until Mirai's arrival shifted family dynamics.

The garden serves as a portal for Yukko's magical encounters with Kun. During one of Kun's jealous tantrums, Yukko manifested as a shaggy human prince, voicing his own grievances about being overlooked after Kun's birth. This form retained canine traits, notably a detachable tail. Removing this tail and attaching it to himself transformed Kun into a dog, causing chaotic scenes where Kun ran wildly while Yukko, forced into pursuit as the human prince, expressed exasperation—highlighting their shared displacement.

Yukko's background reveals he voluntarily chose the Ota family over his biological mother, a decision witnessed during Kun's journey through the family history within the magical tree. Later, Yukko assisted Kun and Future Mirai during the Hinamatsuri incident when the family neglected to store traditional dolls, further cementing his place in their collective experiences.

His significance lies in symbolizing shifting familial focus. Through interactions like his pointed "Now you know how it feels" speech to Kun, Yukko mirrors the child's own feelings of neglect after Mirai's birth, acting as a catalyst for Kun's growing understanding of empathy and family bonds.