I don't know the exact main characters in this novel. However, we can assume that there is a male lead and a female lead. The male lead might be a charming and confident person, while the female lead could be a strong - willed woman. They both get thrown into this unique situation of being 'fiance' for seven days and playing the games which would shape their relationship.
Not having read the book, it's hard to say precisely. But in a love - and - games - themed novel like this, there could be a main character who is a bit of an adventurer, always up for a challenge, and the other main character who is more reserved but is gradually drawn into the wild situation of the seven - day fiance deal. These two would then be the central focus as they navigate through the games and their emerging feelings for each other.