The "Japanese Constitution" and the "Japanese Criminal Procedure Law" establish the status of the accused and grant them the right to remain silent.
The suspect can clearly state "I don't want to talk" or "I want to remain silent" to refuse answering questions from law enforcement officers of the investigative agency.
If the suspect requests a lawyer to be present, the police should wait for the lawyer to arrive before conducting the interrogation. Otherwise, the obtained interrogation records may not be legally valid and cannot be used as evidence for the final decision.
All officers handling cases are aware of these basic regulations, but few actually comply with them.
Coincidentally, Minamoto Tamako is one of those few.
