is Mary Sera's husband and the father of Shuichi Akai, Shukichi Haneda, and Masumi Sera.
17 years prior to the current timeline, Tsutomu Akai was involved in the double murders of Kohji Haneda and Amanda Hughes. What happened to him during and after the incident is currently unknown. Tsutomu was believed to be deceased by his family, however, his body was never found. It was his involvement with the murder case that prompted his son Shuichi to join the FBI in order to investigate what happened to him, and his assumed death led Shuichi to seek vengeance against those responsible.
Before he went missing, Tsutomu sent his wife a message telling her that he had made enemies with "horrible people," asking her to take their children to Japan, and to think of him as someone who no longer existed. Sometime after his daughter Masumi was born, so both Masumi and her father never got to know each other.