In a mountain town where an old legend persists, a fearsome creature known as the Yamatagi Madara was said to have once terrorized the region. This half-human, half-snake entity is now considered a vengeful god, and the western mountains where its shrine stands are strictly forbidden to trespassers. After a heavy storm causes a landslide that destroys part of the barrier, siblings Hinata and Kaoru from the Misogiya family, which has governed these mountains for generations, venture into the prohibited zone out of curiosity. There, they come face to face with the legendary creature, which has the upper body of a shrine maiden and the lower body of a massive serpent. Despite its terrifying appearance, the two children are not frightened. Instead, they grow fond of the demon, giving it the nickname Dara-san and beginning an unusual friendship.

The story follows the daily life of Dara-san as it navigates the modern Reiwa era alongside Hinata, a lazy but strong-willed middle schooler, and Kaoru, her energetic younger brother. Though Dara-san is a powerful deity with a monstrous visage and six arms, its personality is gentle, rational, and surprisingly well-suited to contemporary life. It quickly adapts to activities like summer festivals, sleepovers, and trying out toy models, often serving as the straight man in comedic situations. However, the series balances its lighthearted comedy with horror elements, as the mountain is still home to lingering curses and the severed limbs of Dara-san, which possess powerful magical properties. The siblings' mother, Chiyo, has her own history with Dara-san, having met the deity during her school days when a friend fled from the forbidden mountain.

As the narrative progresses, several arcs explore the deeper lore of the Yamatagi Madara. One major arc delves into the tragic past of Dara-san, revealing it was once a kind wandering priestess who suffered a terrible death by dismemberment at the hands of villagers, transforming her into a snake monster. Other arcs involve dealing with supernatural threats, such as the cursed left arm of Dara-san that spreads destruction, and an incident where a classmate of Hinata is possessed by a mysterious presence. Despite these darker themes, the core of the story remains the heartwarming and humorous relationship between the children and the lonely deity, as Dara-san learns to live freely after centuries of carrying a heavy burden. The series is set to premiere in July 2026, produced by Asahi Production and directed by Masato Suzuki.