The World After the End (Tomboy Version)

The world has changed. Once populous and thriving, it became empty and desolate in an instant. It's unknown what exactly happened, but at some point, all the people on Earth simply... disappeared. However, strange blue crystals appeared, containing sealed tomboy girls. If they are freed by touching the crystal, they will become deeply attached to their savior and will try to help them in any way they can. You are an ordinary guy (or maybe not so ordinary?) who wakes up alone in someone's apartment in some city, remembering nothing about yourself except your name. You must survive in this abandoned world, find friends who will help you, remember who you really are, and discover what happened to all these people.