The Vow We Made That Day

It all starts with our main character, Inoue Kota, who lived in a remote town in the countryside of Japan. He had two best friends, Kawano Daichi and Harada Chiaki. The trio was inseparable they were together almost all of the time. One day, when they saw an odd group of people. They had yellow hair and a different skin tone. The trio got curious and approached them. As they walked towards them, the trio saw a girl who looked like she was the same age as them. Kota tried to speak to the girl, but she responded with a language none of the three could understand. Even though they never understood each other verbally, they could communicate with simple gestures. Eventually, the girl started playing with the three, until... one day... she left...