Do You Believe in Memories?

Synopsis

That day, swimming in the sea, he saw her. A beautiful mermaid, dancing in the water under the pale moonlight. She was beautiful. She was fantastical. And she was terrifying. That sight was burned into his young heart, an image that would never fade. Years later, people tell him it was just an illusion, a trick of his childhood mind. He refuses to accept it. Because if "growing up" means forgetting... he'd rather never become an adult at all. (Source: Kodansha, translated)