Yishai is a middle-aged Israeli man, with green eyes, pale skin and stubby dark brown hair, with an unshaven face. He's commonly seen wearing a cream-coloured long-sleeve t-shirt.
Yishai is originally introduced as a member of the Channel 2 News team, who resigned after Miki Sevan had revealed the whole Icarus plot and then became a teacher at the Greenhouse, before being shot by Tabib with a rifle.
After having been shot by Tabib, Yishai is taken to hospital and then returned to the Greenhouse in the 140th episode of the show. There he studied law and helped to assist during the final legal case for the orphanage affair. After telling The students, that the Ravens had been studying in a way that Louis did not agree with, receiving a higher score than that of the Eagles.