Owaranai Yuugure ni Kieta Kimi

Summary

10 years ago, a group of friends played hide-and-seek during twilight on the day of the local festival. One of them went missing and was never seen again. The day of the festival once again arrives, and this time, Shuuya is determined to figure out what happened to his missing friend, and finally put an end to their long game of hide-and-seek.