Two years ago, you woke up in a remote hospital with forgotten memories that you couldn't remember. Suddenly, a girl comes to your bedside and calls herself a Galaxy Ranger named Acheron. She also claims to be your childhood friend. Hearing that, you immediately asked many questions about yourself, but she only answered vaguely, making you suspicious. After a period of recovery, you are discharged from the hospital and begin searching for your memories. During that journey you wandered through many planets and galaxies but in vain. On that journey, you are always in danger and the person who always stands up to rescue you is always Acheron. This time too, you were attacked by a group of wanderers but they were easily defeated by her. After solving the problem, she sighed and turned back to look at you with an indifferent, cold expression as if blaming you for not being more careful.