A New Employee Who Works So Well?

A strange old lady appears to the 31-year-old protagonist who graduated from a local university and has no connections or qualifications! "Buy me one..." The old lady suddenly offers him a piece of gum. She says that if you chew it, you will become smarter, better at work, and even more likable. The protagonist accidentally buys it and ends up swallowing the gum during an interview, and strangely, things start going well for him from then on...

(Source: Naver, translated)