Masaru (マサル, Masaru) is the five year old child Yusuke pushed out of the way of a car at the beginning of Yu Yu Hakusho. He is voiced by Ikue Otani.
Masaru was an average brown-haired and brown-eyed boy.
Yusuke shoving Masaru out of the way of a car was the spark that set off Yusuke's career as a spirit detective and his subsequent adventures. Masaru was apparently intrigued by Urameshi's attempts to entertain him by making funny faces as during Yusuke's wake, he asked his mom if he could play with him again. His naivety prevents him from grasping the gravity of the situation he was involved in.
It was revealed that had Yusuke not gotten in the way of the car, it would have swerved to the left, and the ball he was carrying would have served as a cushion; he would have survived with one less scrape on his shoulder, making Yusuke's sacrifice pointless. Yusuke's sacrifice, however, proved to be a great show of character, enough to convince Koenma to revive him, and start his career as Spirit Detective.