Haruka blinked a few times as the older boy simply waltzed through the other door.

"Hey! Wait a second!" Haruka shouted, just realizing what had just happened. As she reached the other door, she saw the sewer tunnel. She vaguely took notice of how different this world was to the last one. She smelled the raw sewage as the stench invaded her nose and made her eyes water. And she saw the boy, as he threw a rock into the sewage.

"Wait... please just wait a minute! You can't... you can't go down there alone. What if..." 

Haruka didn't know what if. She had no idea what this world contained inside of it. But there was no way this would be just a walk in the... sewer.

There had to be more to it than just this.