A founding member of the student protest group SEALDs has received a death threat against him and his family.

Aki Okuda, 23, a key member of the group Student Emergency Action for Liberal Democracy who attends Meiji Gakuin University in Tokyo, said on Twitter Monday that he had received a letter threatening to kill him and his family.

"A letter threatening to kill me and my family arrived at my school," Okuda wrote. "Why does my family have to go through this? I don't want to be killed for just stating my opinions, so I've been careful lately when I go to school."