High School DxD, Vol. 2 - manga

Is love in the air between lowly servant Issei and his mistress, the bewitching Rias?!

Reincarnated as a demon by Rias, the school beauty, Issei finds himself in servitude to his devilish mistress. But when Issei befriends Sister Asia, a nun from the Church, which is widely known to be hostile to demonkind, he's practically asking for a target on his back-as Rias is quick to inform him! Worse yet, when the good sister is kidnapped by a fallen angel, Issei rushes to her aid! But little does he know that Heaven plays dirty...!