User blog comment:B214/High School DxD EX/@comment-50.139.232.230-20151108154354/@comment-50.139.232.230-20151108155901

Another thing:The power of nature she gained is basically the result of her training with her mother before she went into deep slumber (the healing is just an extension skill of her nature manipulation, one can say that this is Asia's version of Senjutsu but no use of the Twilight Healing). It is possible that Airi honed it to the current level of mastery through the war.