Girl: You wake up in a castle, and you don't know where you are. There are so many things out of place, and your memory is blurry, so you really just have to connect the dots. It's not that hard once you notice a few key things: Your clothes are gone, replaced by terribly revealing underwear. Oh, and there's a man sleeping beside you. After learning that you've been gifted to this pervert as some sort of toy, you rebel as much as possible.
Guy: You're the Crown Prince of (some kingdom) and for some reason, you’ve been given a slave girl to do with what you please. You aren’t a very nice person, but you aren’t a monster. You do your best to wrangle this girl into submission but she’s like some wild beast.
And things progress from there.
(I have drawn some maps.)
Okay, so a lot of the northern kingdoms (Eskal, Ardany, Essea) worship Twelve Saints and Three Devils. The Saints are all people who once lived, and did great deeds that lived on to teach a lesson. The Devils are the opposite. They're the negatives, people who did horrendous things in life and now control the Abyss, what we might call Hell. We can introduce the deities during the roleplay.
Noxus and Ardany have been warring on and off since they began. Ardany has well-protected lands and an abundance of precious resources that most haven't even discovered, while Noxus, to Ardany, is nothing but a boiling cesspit filled with murderers and liars and cheats. Noxans think Ardanians are as cold as, if not more so, than their country and the frozen wastes to the north of it, and they should come down from their high horse. Ardanians are quite content with their territory. Noxans keep provoking them into war. It's safe to say tensions are high.
Banti is neutral and will either help both sides in times of war or will help no one at all. Kiba is nothing but jungle, allied with Noxus, and home to slave-worked coal mines. Xiang-Bao is allied with Ardany and are famed for their warriors, making Ardany near-impossible to invade except through Oldwood, which is famously dangerous for misleading armies and sheltering monsters of nightmare. Genta is allied with no one and hates the squabbling of other countries. It's too small to invade any other kingdoms, so the poor Gentans must be content with their freezing cold rock in the middle of nowhere.
Ardany is like Russia, Noxus is like America, Banti is most of the middle east, Xiang-Bao is a mix of Asian countries, and Genta/Eskal/Essea is a blend of the U.K. and is mostly like Europe.