The Jisei series is a visual novel series created by SakeVisual for the Microsoft Windows, Mac OS X and Linux platforms.
Each game in the Jisei series plays out as a mystery novel, with the player examine their current location to find clues. The player also can talk to people and get hints. The player can access an in-game notebook to keep track of all clues and hints found so far. As of Yousei, the player can use Kangai's phone to send and receive messages from other characters, serving as a hint system.
Source: Wikipedia, "Jisei (video game series)", available under the CC-BY-SA License.