You don't need a key. You can enter that place. There is a lounge next door to Dongbao. It's best to choose at night. They are all sleeping in bed. On the first floor, you walk from one bed to another, and there is an old man in it (he will tell you the task). I'll tell you how to get into Beiqiu (the map can be navigated! )。 That entrance is on the floor. It's the spiral staircase upstairs in the lounge (the place next to the first floor looks like iron, and there is usually a pile of yellow grass on it)