Ater a couple of hours, I find it quite messy to have companion (s) to aid you in Wo Long and that makes the game easier (To my surprise, I completed one of the boss fights in just 1 try).
So I went to find out if we can remove them and we can! Rejoice! Just use the Willow Branch at the Reinforcements Menu at a Battle Flag. It should be done when you are at the 2nd mission after you have acquired Zhao Yun. Since I've already completed 3 bosses, I'm going to do a restart tonight. I'm glad at least they gave us a choice else I would have probably sold off the game if it's compulsory coop (there are some missions in Nioh 2 that you must do coop) all the way. I would prefer a solo and challenging adventure.
I'm sharing this here for those who want to play a more challenging game or find that the inclusion of companions, makes the combat a little too chaotic.