Basically, these games are like gamebooks you read, with sounds and pictures/movies, and usually they have many different endings.

It’s kind of a mix between a novel and a video game.

Here’s an explanattion from Wikipedia about the game system (it sounds quite interactive):

“The game differs significantly from other sound novel / visual novel games in that players read through and switch around multiple stories that take place in the same timeframe, each seen from a different character’s point of view. Decisions made in one character’s story can inadvertently affect the story of another character in unforeseen ways. The format can be compared to films such as Pulp Fiction, Magnolia or Vantage Point.

For instance, the game opens with a detective (protagonist #1) waiting for a kidnapper to pick up the ransom money, which is being carried by a girl. Another character, a young man out for a walk (protagonist #2), happens to encounter the scene. Protagonist #2 now has a choice to approach the ransom-carrying girl or not; If he approaches, his story reaches a dead end by being wrongfully arrested, but not only that, the detective’s story also reaches a dead end by making the wrongful arrest.[3]

The player’s role is to figure out whose actions are affecting whom, and find the right choices to lead every protagonist to the conclusions of their storylines. The game offers a time chart screen where the events of all the protagonists’ stories are listed in chronological order.

Blue-colored text is interspersed within the body text. The colored text, called Tips, can be selected with the controller like a hyperlink. Tips, when selected, provide a short page of explanatory text, much like a tooltip. Tips can reveal the definition of a technical term, provide some insight on the topic, or just provide a short digression from the story at hand. Red-colored text, also selectable, marks the name of a different protagonist and allows the player to jump from one protagonist to another. Jumping from red text is often the only way to make a character’s story move forward.

The game unfolds in an ten-hour period, which begins at 10:00AM of April 28 and ends at 8:00PM. The game is broken up into one-hour segments. Leading every protagonist to the end of the hour unlocks the next hour to be played.”

These games can indeed be good, but because of the amount of text, nobody wants to translate them, a shame. I played Kamaitachi no Yoru 1 and my Japanese is not very good, yet this game kept me glued to the screen, which is proof of the game’s quality, if it can entrance even someone with beginner level Japanese skills.