Hanasaki Mai ga Damattenai

Every day, bank branches encounter various problems like missing money, information leaks, loan problems & breach of duties. Hanasaki Mai's job is to go there and fix the problems. She is able to do so even though she is just a bank clerk without higher-level powers. Because of her character, Hanasaki Mai will not keep still when she sees a wrong. She's willing to stand up for the side of the weak, regardless of the relation between the top and bottom factions of the bank.
(Source: AsianWiki)
~~ Adapted from the novels "Fushoji" (不祥事) and "Ginko Somu Tokumei" (銀行総務特命) by Ikeido Jun (池井戸潤).