Mutsu, who was kept under restraint in Yamagata Prison, busily wrote letters to his wife Ryoko; on the other hand, he wrote a book and also devoted to translating a work by Bentham, a utilitarian philosopher of England.
山形監獄に収容された陸奥は、せっせと妻亮子に手紙を書く一方で、自著をあらわし、イギリスの功利主義哲学者ベンサムの著作の翻訳にも打ち込んだ。