Every day, bank branches encounter various problems like missing money, information leaks, loan problems & breach of duties. Mai Hanasaki'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, Mai Hanasaki 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.