Sweet Fuse is a mystery and romance visual novel in which the player assumes the role of Saki Inafune, as she plays through seven days of death games. Much of its gameplay is spent on reading the story's narrative and dialogue. The player will be prompted on occasion to pick what to make Saki say. Picking the correct responses will sometimes given the player an "affection point" for a particular character which raises that character's affection level. There are moments during which Saki will become irate, indicated by the screen shaking and turning red, and the player will have to choose between having her restrain her anger or letting it out.

"Explosive Insight" sections take place when Saki must find a solution or an answer to a problem. Saki recalls the situation to herself, with a number of keywords and phrases in her thoughts highlighted. The player can pick up to three highlighted words or phrases to select, and the player prompts Saki's epiphany if one of their selections is correct.[1] If the player does not select the correct phrases, a bad ending will usually occur and they are prompted to try again.

The game follows a branching plot line with multiple endings; depending on the decisions that the player makes during the game, the plot will progress in a specific direction.

Saki Inafune, niece to legendary game developer Keiji Inafune, can’t wait to visit her uncle’s new theme park. She’s been invited to the opening day ceremonies, and is looking forward to a day of fun and excitement when suddenly Count Hogstein - a villain as corpulent and cliché as he is evil - blows up the Ferris wheel, takes the park management hostage, and declares the beginning of a deadly series of games.

Desperate to save her uncle, Saki volunteers to be one of the participants in Hogstein’s games, and finds herself thrust into the midst of excitement very different from what she’d expected when she woke up that morning. She’ll need all of her cunning, determination, and exceptional insight to get herself and her fellow participants - all available bachelors - out alive and maybe, with a little luck, find love along the way.