The Azusa River flows quietly through the entire Kamikochi region, driving changes in the ecology and scenery of the entire environment, giving a sense of continuous renewal, and providing moisture and vitality to various forest plants and animals.
There are doubts about whether the "Azusagawa" on Google Maps is actually the Azusagawa River.
Looking at the mountains from Matsumoto, you can see Mt. Norikura, but not Mt. Hotaka.
The river flowing down from Mt. Norikura is the Ono River, and the area around Hata was Ono Manor and Ono Pasture during the Heian period.
Mt. Aiho (the name on the Gifu side of Mt. Norikura, and the origin of the name Abo Pass) is in Ono District, Gifu Prefecture.
Mt. Norikura was recognized as a mountain pass during the Heian period, and the god of Mt. Norikura is mentioned in the Nihon Shoki (Chronicles of Japan).
The Kamikochi area of Mt. Hotaka was used as a mountain pass during the Sengoku period (Warring States period).
The name Azusagawa only appears in history during the Edo period, and it refers to the area slightly downstream from Hata.
The Kamakura period's Sasage (Azusa) Manor was downstream, around the current Matsumoto Interchange.
The area near the interchange is the old course of the Azusa River, and the place name is "Kurekino," which was a lumberyard during the Edo period.
Perhaps the area where the river passes through Sasagesho is the original "Azusa River."
The river flowing through Kamikochi during the Edo period was the "Kamiguchi River."
If felled timber was floated down the Kamiguchi River, it would end up in Kurekino on the Azusa River, but I don't think it's correct to call the Kamiguchi River or the Ono River the Azusa River.
Just as the Azusa River isn't called the Shinano River, I don't think the rivers in Kamikochi and Hata are the Azusa River.
I think it would be better to clearly define the regional boundaries of the rivers.
The Azusa River becomes the Sai River downstream, and then the Shinano River at the prefectural border.
There is also a Sai River in Kaga, but its lower reaches flow through Onosho in Kaga.
Is there any connection between the two Sai Rivers?
The Azusa River, originating east of Mt. Yarigatake in the Hida Mountains, flows through Kamikochi, forming an alluvial fan in the Matsumoto Basin. It then merges with the Narai River to become the Sai River, and near Kawanakajima, it joins the Chikuma River (the Nagano Prefecture portion of the Shinano River).
Near its source in Kamikochi, the river's clear and beautiful flow is striking, forming the core of the Kamikochi landscape alongside the surrounding mountains, including Yarigatake and Hotaka. The bridges spanning the Azusa River in Kamikochi, from downstream, are the Tashiro Bridge, Hotaka Bridge, Kappa Bridge, Myojin Bridge, Shinmura Bridge, and Yokoo Ohashi Bridge. Each of these bridges offers a unique and charming view. Furthermore, in the early morning, mist spreads across the river's surface, creating a fantastical scene.
