User blog comment:B214/High School DxD EX/@comment-50.139.232.230-20151108154354/@comment-50.139.232.230-20151111043744

A speculation that how Fafnir lend his power when Airi wears her armor is not the regular Fafnir, but the Pantsu Dragon King's more controlled Outrage Mode, which explains her OP raw strength in that form.