Ayameiro no Natsu

A story based on real events.
On September 18, 1988, the mountain Yamatsu village located on the prefectural border between Iwate Prefecture and Akita Prefecture collapsed due to a large-scale earthquake. The rescue activity was significantly delayed because of a typhoon. As a result over 300 people were dead or missing.
Initially declared as an earthquake, the disaster did not involve somewhat strong earth shaking or land slides which posed a lot of questions.
Main character is the descendant of the Yamamori clan protecting the village since Heian times. This is a story of him returning to the village as an adult and experiencing this disaster that's implied to have absolutely different sources...

[From vndbreview]