Strive to add distinct elements to your game/story which will be obvious from the very first scene. It's possible to create a multi-path game with an Official Couple.
This might even make the other characters Pretty Freeloaders.
Stereotypes: some character lists in bishoujo and otome games can seem like checklists of fan-favorite character types.
(Patient Childhood Love Interest, Meido, Ojou Sheltered Aristocrat, Not Blood Siblings, Troubled, but Cute, Token Mini-Moe...) Add some unique-but-not-bland characters, or at least add some variety.
Maybe you can even go as far as to create a story in which the two people are more than just casual acquaintances at the beginning.
If your setting is realistic, then make sure you can portray it in a way that the audience will find interesting.Perhaps you are interested in creating a cute story in which the main character can end up with one of several love interests.Maybe you want to prove to the world that you can make a full-blown Dating Sim without problems like illogical choices (or gratuitous sex).It's possible to present the audience with a character who seems like a stereotype at first, and then introduce complications as the story goes on.If your story takes place near a school, and nearly every important character is under twenty years old, then there's a chance that your story may seem trite even if it's original. Make sure any Meet Cute scenes are not just random occurrences.