As they keep fighting Captain Antonio, they feel how powerful the injection of chicken blood is. It not only increased the damage they deal on the boss but increased their survivability as well.
On Hell Mode, the boss attack and defense are higher than on other modes, thus without this buff, the boss would be taking very little damage from their attacks.
Ye Yan used his closed fan to deflect the boss attacks and open to attack or defend when needed. Sometimes, Ye Yan couldn't deflect Captain Antonio's strikes and need to use his fan as a shield.
To defend, Ye Yan opens his fan and puts his left hand behind it as support to stand the boss's attacks.
The fan is the most suitable weapon for Ye Yan. It can attack, defend, help deflect attacks, and still can be used to fan himself in an elegant way. That's why, if he didn't find another fan, he will just pay a forger to upgrade it, using some of the material he has stored.