The game was just released by mangagamers. It's an all ages Kotori spinoff of the first Da Capo game.
Da Capo Innocent Finale
She loved you, but you chose another. What would have happened in Da Capo if you had fallen in love with Kotori instead? Da Capo IF (Innocent Finale) gives you the chance to provide Da Capo's Shirakawa Kotori with the happy ending her fans have wished for.