User blog comment:SpookyBoogie27/Light Novel Spoilers/@comment-33447191-20130131105522

Great news for Irina Shidou fans!!

Ah. Sorry I forgot to mention one thing which might be important. Angels can have sex and create babies without falling. They just have to purify themselves and do some kind of ritual doing it. And they cant have ill thoughts while doing it. I can't remember the actual details but it was somewhere in Volume 14. So Irina joining the harem wont be a problem.....I think.

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