Aokana: Four Rhythm Across the Blue is a romance visual novel in which the player assumes the role of Masaya Hinata. Much of its gameplay is spent on reading the story's narrative and dialogue. The text in the game is accompanied by character sprites, which represent who Masaya is talking to, over background art. Throughout the game, the player encounters CG artwork at certain points in the story, which take the place of the background art and character sprites. The game follows a branching plot line with multiple endings, and depending on the decisions that the player makes during the game, the plot will progress in a specific direction.
There are four main plot lines that the player will have the chance to experience, one for each heroine. Throughout gameplay, the player is given multiple options to choose from, and text progression pauses at these points until a choice is made. Some decisions can lead the game to end prematurely, which offer an alternative ending to the plot. To view all plot lines in their entirety, the player will have to replay the game multiple times and choose different choices to further the plot to an alternate direction. Throughout gameplay, there are scenes with sexual CGs depicting Masaya and a given heroine having sex.