Mitsui Sumika to Shikakui Akuma

is a Japanese light novel series written by Takato Hyousuke, with illustrations by Pudding Pudding. The series began publication on October 10, 2011 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
No job, no money, no girlfriend, Yuriko Hishimi has a debt of 10 million yen!

It was a mysterious beauty, Sumika Mitsui, who suddenly appeared in front of Yuji who was in trouble without being able to repay a large amount of debt. She quickly repays Yuji's debt and says, "Work for me." For some reason, Yuji, who had to pay off his debt while working under a beautiful woman, was happy because he got a job.

That profession is the "debt collection" of a credit card company ── !?