High School DxD: Asia & Koneko's Secret Contract!? (Manga) (Book) 
Manufacturer: Yen Press
The naturally clumsy Sister Asia and taciturn cutie Koneko form an unlikely devilish duo in this spin-off of the mega-hit High School DxD! The two head out to answer summons from humans with requests, but...th-th-they want Koneko and Sister Asia to do what?! These two little devil beauties get to work! But can they really fulfill every desire?!