User blog comment:SpookyBoogie27/Light Novel Spoilers/@comment-94.129.209.103-20130207081756/@comment-6341273-20130207083216

It's been hinted for a long time and in volume 13 in one of the short stories wich takes place after volume 7 he used the gender changer ray gun to turn himself into a girl and nurse Issei but due to some clumsy attempts he ended up on top off Issei just at the time when the girls entered never the less they were quiet shocked if that word would exprese it.But otherwise Kiba did not state that he has romantic feelings towards Issei but it's still quiet likely.