User blog comment:SpookyBoogie27/Light Novel Spoilers/@comment-1359322-20130504051812

(「赤龍帝ちーん♪　ちかれたんで癒してほしいのよねー」 黒歌が突然、俺、兵藤一誠に抱きついて、俺のほっぺに自分のほっぺを擦りつけてきた. ) 謎の集団による駒王学園襲撃から数日、俺はレイヴェルと自室で、真面目に契約相手となる魔法使いの選抜を進めていたハズなんだけど……. 気づけばいつものユルユルで騒がしい日常. そんな中、朱乃さんがリアスと出会った頃の事を語り始めた. それは辛くて切なくてそして優しい、二人の絆の物語――. 悪魔な学園ラブコメバトルファンタジー、君は《絆》を感じたことはあるか?

Well since i'm lazy to do a full translation i'll just summarize it.

The part in the is a story about Issei and Kuroka, something about Kuroka doing the healing session for Issei.

The 2nd part, Issei is going through his Magician pact with Ravel until he notices that his surrounding his lively as usual. Then suddenly Akeno starts talking about when she and Rias met.

It was also written that Akeno and Rias' story being painful, sad and kind, a story that tells the bonds between those two.