Nuko is a mysterious white creature that appears in the anime and manga series Girls' Last Tour. Its exact origin is unknown, but it is discovered by the protagonists Chito and Yuuri in the ruins of an abandoned battlefield in a different part of the megacity. The name Nuko was provisionally given by the girls when they first encountered it; the name is derived from the Japanese word neko meaning cat, as they initially mistake it for a cat. In some translations, Nuko is referred to as Cut or Ket.

Nuko has an elongated, catlike body with four small limbs and no distinct tail or ears. It is a sentient being capable of shape-shifting, allowing it to alter its form to fit into tight spaces, activate mechanisms, bypass electrical locks, and operate computer programs. This ability proves essential for navigating the abandoned technological ruins that Chito and Yuuri explore. Nuko consumes unusual materials as food, particularly bullets and bombs, which it appears to eat with enthusiasm. It communicates through radio signals and can learn language, but it cannot speak audibly unless a receiver is nearby.

Nuko is characterized by a playful and curious disposition, often displaying a childlike wonder as it explores the world alongside Chito and Yuuri. It does not speak in human language but vocalizes with sounds such as nui. Despite its non-verbal communication, it forms a clear emotional bond with the two girls, showing signs of attachment and reluctance when the time comes for them to part. Its motivations center on companionship and assisting its friends, though it also follows the signals that lead it back to its own kind.

In the story, Nuko joins Chito and Yuuri during the latter part of their journey. Its shapeshifting and radio abilities become key tools for the girls, helping them unlock doors, access sealed areas, and decipher remnants of the old world technology. After following a signal to a nuclear submarine, Nuko reunites with other members of its species, known as Eringi. It is revealed that Nuko and its kind have the ability to consume and stabilize unstable energy. Though Nuko appears reluctant to leave Chito and Yuuri, it departs with the Eringi as they ascend into the sky. Prior to their departure, the creatures inform the girls that they are the only two humans remaining on that level.

Nuko's most significant relationships are with Chito and Yuuri. The bond that develops between the creature and the two girls provides emotional warmth and lightness amid the desolation of their world. Nuko acts as a bridge between the girls and the remnants of past civilization, often catalyzing moments of reflection and discovery. Its presence also serves as a source of comfort and comic relief, reinforcing the themes of loyalty and companionship that run through the series.

Though Nuko appears only in the later portion of the story, its role is impactful. It helps Chito and Yuuri access areas and information they otherwise could not reach, deepening their understanding of the world that was. Its departure marks a turning point, as the girls continue on alone, now aware that they are the last humans on their level. In a later work by the same creator, Nuko reappears in a different form, suggesting its mysterious nature extends beyond the original story. Overall, Nuko stands as a symbol of hope, adaptability, and the quiet connections that endure even in a world stripped of most life.