The amount of Chemistry you have, which you get by making choices during the Story and through raising your Charm, determines what ending you will get.
There is only one ending. You will need 30,000 Wife Points and 150 Chemistry to get it.
You will not be able to get the Super Happy End on making the right choices alone (unless you play the story during Double Chemistry Fever). Choosing all the right answers will only give you a total of 140 points, so you need to have at least 10 Chemistry from raising your Charm so that you can reach the 150 points needed for the Super Happy End.
A: Squeeze her hand harder.
[Be My Princess: PARTY] New Story Gacha Coming Soon: Secret Garden ♥ Soaked in Jealousy!?