日本語 Japanese Ask Questions Thread 8

If you have a question about the language, ask it and fellow 4channers might see it and answer it for you.

英語でも日本語でもOK
日本の方からのご協力も大歓迎です

See >>2 for recommendations of
■ useful software
■ dictionaries
■ sites to get media
■ other resources

See >>3 for links to previous threads.

NOTE: For those new to the text boards, know that they work a little different from the rest of the site. If you click on the thread title you are only shown the first 40 posts. Use the "Entire Thread" link at the bottom of this thread to see the rest.

I cannot grasp the meaning of としてさ and わけだろ in the following sentence. As far as I can understand としてさ here means used to change the topic and わけだろ is somethng about common knowledge or information?
By the way 夜の世界 in this VN is about the phenomen when in the night time, school changes in to the other magic school(yeah I know, my explanations sucks) and another students suddenly appears there. 
満琉「夜の世界もそうだけど、生徒も謎だよな。」
小太郎「え？」
満琉「夜の世界が裏側だかどこからか召喚されているとしてさ」
満琉「夜の生徒ってなぜか、ここに召喚された学園に通ってるわけだろ」
満琉「その裏側の世界とやらから来てるのかな」