Yami to Boushi to Hon no Tabibito

I have always thought that this normal peaceful everyday life would go on forever. ---until the day I met with that incident. Even if I had a fight with her, everything would be fine if I just apologized. ---until she was abducted by a huge red dragon that evening. And, when I realized it, I was in a weird library. At first, I could not grasp the situation, however, soon I found out that library was a magical library with books which hold everything in the World. I tried to return to the original World ---where she is in--- however, the World Book I was in was partly destroyed and I could not return. In attempt to protect my own World, to rescue her, I set off on a travel to fix the Book.