Linh is an impoverished village girl who finds herself accused of a crime she did not commit and sentenced to be judged by the local village snake god. When she's thrown into a snake pit, a white snake approaches her and offers to save her...for a price.
The white snake is revealed to be a shapeshifter named Ai, who decrees that Linh will serve as her companion in return for being rescued. Complicating matters is the arrival of Jinhai, a female monk who says that she wants to help set Linh free and also seems to have some history with Ai.
Though Linh desperately wants to go home to her family, she also can't help but feel drawn towards both Ai and Jinhai. The longer she stays with the two of them, the more Linh begins to question her understanding of life and what it means to be human.
Mizuchi contains examples of:
- And the Adventure Continues: The "Journey to the West" ending has the three heroines deciding to leave their mountain home to avoid the villagers seeking to use Ai's power and going westward to see the world.
- Distant Finale: One of the endings shows Ai and an immortal Linh in modern times, having been married for centuries and holding yet another marriage ceremony to celebrate their undying love.
- Fantasy Counterpart Culture: Though none of the countries are actually named in-game, they are all heavily inspired by Asian countries. Linh lives in a country heavily modeled after Vietnam, and Ai comes from a country heavily modeled after Japan.
- "Freaky Friday" Flip: At one point in the story, Ai's power causes her and Linh to switch bodies for a day. Jinhai reveals that she and Ai also switched bodies at one point, though under less pleasant circumstances. Ai doesn't remember this because she was unconscious.
- Happily Married: The Future ending, where Ai and Linh are married to each other and even hold wedding ceremonies multiple times throughout the ages.
- Homosexual Reproduction: Ai tells Linh at one point that she wants Linh to bear her children. When Linh points out that they're both female, Ai mentions hearing of a species of lizard that is capable of reproducing between two females. In the "Future" ending, Ai uses partheogenesis to create two daughters, Mai and Jun, though she also finds a way to actually impregnate Linh.
- Immortality Inducer: Jinhai reveals that Ai can turn people immortal if she takes a lot of their blood. Jinhai herself was turned immortal through that very method, and this is a fate that can potentially fall on Linh.
- Legendary Carp: Best seen in Jinhai's endings when Ai, who was originally a carp, transforms into a dragon.
- Meaningful Name: Ai's name is a bit of a layered version. "Ai" means love in Japanese, and it has a synonym in the form of "koi," which can mean both "love" and "carp," the latter of which is Ai's original form.
- Our Dragons Are Different: In Jinhai's endings, Ai eventually turns into a giant dragon in order to drive off the villagers of Osin. Said dragon form is capable of using both ice and fire to devastating effect.
- Our Mermaids Are Different: One of Ai's forms is a blue-scaled mermaid, which she uses whenever she wants to feel more relaxed or make an escape. In this form, her personality becomes more serene and she gains the ability to use her enchanted voice to control others.
- Recurring Dreams: Linh frequently has a dream of being underwater and seeing a large hand near the surface. She's actually seeing Ai's memories from when the latter was originally a carp.
- Snake People: Ai is often seen in her naga form, where she has the upper body of a woman and the lower body of a snake. She prefers this form for its greater mobility, though she also exhibits more aggressive tendencies when taking naga form.