The goal of a dating sim is to raise your Relationship with characters and after falling in love, to have a happy ending with them.
Raising your Relationship can be done by talking to them, giving them gifts and going on dates.
Once you have enough successful dialogues with the character, a message letting you know that you can now go on dates with the character will appear.
Daichi is the only character who will start out dating someone else.
Daichi confesses in Spring if you watch him play basketball. If you date a character and later on begin to date someone else, the pervious love interest will become an ex-boyfriend.