Natsukashiku Omou Kimi wa Dare

Ten years ago, he used to play a lot with a girl named Oto-chan. They promised to marry if he grew taller than her over the years. With modest but indelible memories in his heart, Hajime Aoima led a normal high school life—until the "promised day" arrived with Oto-chan. Upon reaching the tree where they had made the promise, what Hajime sees before his eyes is an amazing spectacle. A nostalgic and captivating suspense story full of charm and horror! (Source: Kodansha, translated)