A third year middle school student and the younger brother of Ryuuta Saki. He looks very much like his older brother and is often called "Saki number two" (佐木2号, Saki ni-gou) by Kindaichi because of it. Like his brother, he's obsessed with keeping a video record of his surroundings, which often ends up helping Kindaichi solve his cases. He's been enthusiatically helping Kindaichi out this way ever since his first appearance is in the "Kindaichi the Killer" case, where he claimed his late brother appeared in a dream requesting him to do so.

As Ryuuta is still alive in the anime adaptation, Ryuuji's never appeared in it and all his appearances in the manga are given to Ryuuta instead in the anime.

No voice actors have been added to this character. Help improve our database by searching for a voice actor, and adding this character to their roles .