How can I improve my courage? Will watching more scary ghost movies work?

I don't think so.

There are a few guys around me who really like to read martial arts fantasy novels, but they don't have a warrior's demeanor when it comes to dealing with people, instead they're wishy-washy.

Horror movies only make you get shitfaced by yourself while walking at night.

I suggest you watch some tragic movies first to improve your sense of luck, such as Kim Bok Nam Incident, The Day After Tomorrow, When Happiness Knocks, I Am Legend, 1942.

Then go to the grocery store and haggle and argue with the food seller.

Go to the game hall to dance in the street in front of a large crowd, or follow the amazons to dance in the square.

Then finally try to sell insurance.

Take it all in stride, and the guts come naturally.