Kohakuiro no Yuigon ("Amber Testament") is the first in the row of detective games starring the fictional Japanese private investigator Ryūnosuke Tōdō. The events of the game take places in Japan in the year 1921, and Tōdō must investigate a mysterious murder of a rich man in his own mansion. The deceased had many relatives, and its the detective's job to find out which one of them (if any) has committed the murder.
The game plays mostly like an adventure with light simulation elements. The interaction is done with menu commands, focusing on conversation topics. The protagonist has to talk to the mansion's inhabitants about other people and hear their opinion concerning the crime, unlocking new topics as he gathers information. Rooms can and should be searched for clues as well. In his own room the detective can view dossiers and evidence.