Secret Summer is a simulation game developed by SuperWriter that puts you in the shoes of the main character, who is trying to find a way back to his mother and three sisters after being separated to be trained as the successor to his father's business. The game is set to be a family reunion, but it comes with its own set of problems. You will have to face different challenges, including your very serious and ambitious 22-year-old sister Zoe, your free-spirited 23-year-old sister Leanne, and your 18-year-old sister Coral, who has a strong dislike for a specific reason.

As the main character, you have full control over your decision-making, which includes deciding how to interact with your family members, being stricter or more understanding, and choosing which characters to spend time with. However, your choices have consequences, and rejecting to spend time with a character or choosing the wrong choices may disable you from their route and all future content with them. The game allows you to name your own character, define the relationship within the game, and replay the game to access different content.