other than the characters in the party, who can be in the sleeping chamber?  I'm new to this game and want to make my harem ;_;

It can vary depending on your choices.

In the menu, you have the "CG room" option. Try to get all of these characters, and you pretty much have your harem. :D

all the characters in the "CG room" can be in the sleeping chamber?  well, my room will be like a shelter xD