Prisoner's postcard by artist Sadamichi Hirazawa. Died in prison due to wrongful conviction in the Teigin Incident. The back is a thank-you note from the artist.

This is a picture postcard with a letter of thanks from the executed prisoner Sadamitsu Hirasawa, an artist suspected of wrongful conviction, who was analyzed from that perspective by Seicho Matsumoto. The postcard is made of thick Japanese paper. To conceal the addressee's address and name, a memo from Mr. Toshio Ishii, who was Hirasawa's supporter, has been overlaid. According to Mr. Ishii, Kōsai was the pseudonym Hirasawa adopted after his arrest.