READ CAREFULLY BEFORE APPLYING
MasterSlave
Your character will be mark as MM or SS (obviously since Master is the Moon and Slave is the Sun ) For Master, you may buy the Slave you want by telling the admins and it will cost you 100 Points for owning and you must have your own Mansion or House first before you buy them. PM admin if your decide to change the Master/Slave or buy them.
Master please be nice with your slave, at least do not neglect them!
Prince-Citizen
If applying this, your character will mark as MP, SP or EP. ThisTheme wasnt necessary that you need to be A TRUE PRINCE, you may be a prince-in-training. You're from a royal family therefore you need to act one. You can marry either with other Prince or even with your people. 
Brother x Brother
Your character will mark either MB, SB or EB for this theme. Technically this theme involves between siblings
( the older, Hyung and the younger Dongsaeng ). Plots or winging are all depend on your own liking but better for plotting since it will be much more easier.
♦Regardless of your chosen theme, these three can be rp-ed together. Example if you chose sibling's Theme, you may rp with someone that in different theme like MasterSlave or Prince-Citizen.
Just plotting it well and you may end up paired with different characters in different theme