>>14771929I imagine she'd be in a game similar to Fire Emblem, so based on that:
Kiara would be a recurring miniboss, constantly reviving and trying to thwart the player. She's not part of the bad faction you have to beat, her real motivation is that she's jealous of the MC having all those cute female party members. As the game progresses, depending on which girl(s) you've had in your party during your encounters, she tries to get closer to them by various means, like gifting rare gear to them, offering them to join her and ditch the hero party (will not succeed except for very specific situations, but if she does, that party member won't be available), or she offers to join your party instead after enough affection points have been amassed. She gets more difficult in fights the more males you have in your party, but she'll raise more affection points that way towards the remaining girls in the party. On the other hand, you can cheese her any time by bringing an all-female party in which case she refuses to fight and lets you go, but you gain no XP for that.
Once she's on your side, she won't stop gaining affection towards your party members, granting bonuses based on the girl she's in love with and in the ending she'll marry her. Sometimes she does get affection points for males as well which gives rare bonuses, but reaching that state requires the player to balance her affection points in a way that she doesn't get infatuated with any single girl.
Players like her in their party because she auto-rezzes after a certain amount of time if she takes fatal damage and she's a good frontliner/vanguard capable of both dealing and receiving decent damage, and also deals a lot of magic damage, which makes her pretty strong and worth to try and get as a member.
Excuse my autism, but the concept seemed too much fun to pass on. 
