Naki is a red ogre living in isolation on Monster Island, separated from human society by a history of conflict. Like other monsters, he fears humans despite their non-threatening nature. His parents were killed in the human-monster war roughly 200 years ago, leaving him with deep resentment and trauma. This past shapes him into a grumpy, difficult-to-please ogre, unpopular among his kind and distrustful of both other ogres and humans, leading to a solitary life. His only consistent friend before the story's events is the blue ogre Gunjo.

Naki's character transforms after encountering Kotake, a human child who wanders onto the island. Despite his ingrained animosity, he reluctantly cares for Kotake. Through interactions with the child and his ongoing bond with Gunjo, Naki gradually opens his heart, showing tenderness and forming a genuine connection. This period marks a significant shift in his demeanor.

When Kotake wishes to return to his human family, Naki, now concerned for the child's safety, selflessly decides to personally escort him. However, villagers react violently upon seeing Naki with Kotake, attacking the ogre and forcibly separating him from the child. This rejection plunges Naki into profound depression after losing Kotake. Witnessing this despair, Gunjo makes a critical intervention resulting in permanent separation between the two ogres, a sacrifice highlighting the enduring impact and irreversible consequences of Naki's emotional journey.