Chapters up to 7 in each group have only one correct choice. An additional three chapters, known as 'Heaven' scenarios, act as epilogues to the main story and can only be unlocked when all correct choices are selected.
Otherwise, there are a total of 30 unique chapters for each character, with these 30 being split into three groups: Dark, followed by Maniac, and finally Ecstasy. Because of this set-up, the only scene which is repeated throughout each character's route is the prologue.
The game begins with Yui selecting one of the vampires instead of interacting with them simultaneously until it branches off into specific routes, like most visual novels. Unlock chapters by choosing the correct choices.