Mina Soko ni Sumu Sekai

A rural town rich in nature beauty lies in a deep mountain gorge. At the source of a mountain stream, it's as if "another world" is reflected in the mirror-like water. The main character, Mio, is a cam-girl living in Tokyo. Every summer, she returns alone to the town where she was born and raised. During the summer vacation of her senior year of high school, Mio is enjoying playing in the river with her old friends as usual, when suddenly she discovers the secret of her childhood friend Kohei. The incident will eventually shake their relationship and their "world." A suspenseful coming-of-age fantasy colored by dazzling sunlight and limpid water.

(Source: Alphapolis, translated)