User blog comment:SpookyBoogie27/Light Novel Spoilers/@comment-33447191-20130204072232

If they are adding the short story which has been mentioned in the main volume, then the following are those short story which may appear in Volume 15.

-Mahou Shoujo Ria☆For Real!? (The old sub title of Volume 15. So high chance of being included in Volume 15)

-The Sun is a Oppai! (The short story where Poseidon appears)

-The Record of Chichiryuutei's pleasured trip (Vali's adventure and Crom Cruach is mentioned)

-The Decision of the Student Council (Issei joining the Student Council)

-The Love song to the reincarnated Angel (Irina's short story and Griselda appears)

-Let's Go for training! (Akeno's short story. All of the leaders of the Fallen Angels appear and are named.)

Though since there will be Kiba's past story included in Volume 15, only 4 or 5 of the above short stories will be included I guess. And since Fujimi Shobo loves making money, they will most likely release a short-story volume AGAIN next year.....

- (Info. from Code-Zero/n0m@n or Shin Code-Zero)