Natsu no Kagerou

Natsu no Kagerou (なつのかげろう) is a collaborative game developed by Ryukishi07 and Twilight Frontier. The story follows a boy named Kousuke who reunites with his childhood friends, Sae, Wakana, and Youko, as he returns to his remote hometown of Miwata Village. A demo was released in 2011, however the project has since been abandoned. Ryukishi07 adapted much of the story for the manga

Gameplay
Natsu no Kagerou was advertised as an adventure horror open-world game. The player assumes the role of Kousuke and explores the remote Miwata Village over the course of four days. Gameplay is divided into day sections and night sections. During the day, the player is given several minigames based around improving Kousuke's relationship with the three heroines. At night, the player must survive encounters with malevolent spirits called mōryō.

Development
The game was first announced on Twilight Frontier's official website on April 1, 2010. Ryukishi and Twilight Frontier had previously collaborated on the 3D fighting game Higurashi Daybreak. According to Ryukishi's production diary post on April 2, 2010, he was first told about Natsu no Kagerou after the completion of Daybreak and started working on it. He was asked to make a horror game similar to Siren.

The scenario for the game was written by G. O. of the doujin company Blank Note, known for creating Himawari. According to his own production diary post on April 3, 2010, G. O. was given the project by Ryukishi.

A demo of the game was released, but for unknown reasons a complete version never came out. The game is still listed on Twilight Frontier's list of products, but with an unknown product number.

Ryukishi's later manga Hotarubi no Tomoru Koro ni is considered a revival of Natsu no Kagerou.