On a hot summer day, Yuuki and his family were celebrating his birthday in the mall. But when they were walking at the mall, a portal suddenly appeared and a guy came out of it. Both Yuuki's parents had a fearful expression on their faces as if they were looking at someone that came back from the dead. What do you think will happen? In this story, you will spectate Yuuki Tenshin, which is the main character. You will follow in his footsteps and be able to feel his hardships, joy, victory, and cheers in celebrations of his adventures. I welcome you... to the other world.