More than 3.6 billion people globally have no access to safe toilets. Of them, 500 million must defecate openly. Japanese engineer Daigo Ishiyama, who works for a water and housing product manufacturer, developed a revolutionary, simple toilet for areas lacking sewerage. By late 2021, the toilets had improved hygiene for over 25 million people in over 40 nations. Youths discuss with him how he is contributing to Sustainable Development Goal 6, Clean Water and Sanitation, and the problems he faces.