Age: Unknown, Estimated 35 years old
Occupation: Police Officer
Alternate Name: Fourth
Likes: Justice
Height: 183 cm
Weight: 68 kg

Keigo Kurusu is a police officer, so it follows with reason that his diary relates to his work. The "Investigation" diary gives Keigo information of future crimes and activities committed anywhere within the prefecture he is assigned to. Whether or not this means his diary can record events that will happen simultaneously in different locations is still up in the air. Its major flaw is a location issue; his diary is rendered useless at predicting anywhere outside his patrolling district.