Yukko (ゆっこ, Yukko) is a minor character of The Promised Neverland. She is a Mama and caretaker who runs an unknown plantation at Grace Field House . She becomes Phil's caretaker after Grace Field House Plant 3 was burnt down.
Yukko is a fairly tall, slender woman in her middle age with light-colored eyes. She has short, blonde hair tucked behind her ears and short bangs framing her forehead. She dons the standard uniform for Mamas in the plantations, which consists of a black dress with a white blouse underneath it and a white apron over it.
Like all the other Mamas, Yukko was highly trained to become one. In her Mama persona, Yukko puts on a motherly, loving, affectionate and kind-hearted facade whenever she is around the orphans. Hence, her foster children love her deeply. However, it is implied that like Isabella, Yukko shows much detachment to the children's tragic fate, as she shipped Simon off with a smile on her face. Additionally, after suspecting Phil of knowing the truth, she decided to investigate him by calling Andrew, showing that she is unhesitant in taking down those who stand in her way.
Taking care of the orphans living in the House; feeding them, washing them, playing with them – Yukko went through the same routine every day in one of the premium farms she runs, an orphanage where she acts as a substitute mother to all of the children.
Not long after Phil, Sherry and a couple of other orphans from Grace Field House were sent to live with her, Yukko immediately acknowledged Phil to be one of the smartest children in her orphanage. She also accompanied one her children, Simon, to get shipped off and ultimately killed by the demons. After some time, Yukko started to notice Phil's strange behavior as he was often seen in a sad and depressed mood. Eventually, she grew suspicious towards him and called Andrew to visit Phil and investigate.
- In one of the colored pages of Chapter 51, a back view of Yukko could be seen. The color of her hair appeared to be brownish-red. However, later in the colored pages of Chapter 72, her hair color is changed to blonde.
- Nevertheless, Yukko's hair color is considered blonde during her official appearance in Chapter 100.