Nishuume no Boku wa Kimi to Koi wo Suru

In the summer of my third year of high school, Matsuri Tokiwa went missing. She was the first girl I ever fell in love with. I turned twenty, still unable to accept the harsh reality, when for some reason time turned back to the spring of two years ago. While savoring the joy of being able to see her like it's only natural, I confessed, went on dates, and did things that I would never have done the first time... But summer is my time limit. Does she have an idea of why she disappeared? I don't want to lose her again.

(Source: Kadokawa, translated)