What a Friend We Have in Jizōs 31

A samurai could divorce his wife with approval from a superior, but divorce was a rare event for a variety of reasons, most of which were covered by Article 28 of the Reform Edict of Taika of 646:

   The seven grounds for divorce of a wife by her husband: 
     1) if she is childless (e.g., without a male child); 
     2) if she commits adultery; 
     3) if she disobeys her parents-in-law; 
     4) if she talks too much; 
     5) if she steals; 
     6) if she is jealous; and 
     7) if she has a bad disease. 
   In all cases the husband must write a notice of divorce which 
   must be signed jointly by the parents and near relatives. Those 
   who cannot write must make their mark.
   Even when there are grounds for divorce a wife will not be sent 
   away in the following three cases: 
     1) if she has maintained the household during the period of   
         mourning for her parents-in-law during which time the 
         husband could not work;
     2) if since marriage the household has risen in status; or 
     3) if there is nobody to receive her (i.e., if there is no member of 
         her family or other sponsor of the marriage to whom she can 
         return). 
   But these exceptions shall not apply if she has been guilty of a 
   grave offence against piety or of adultery or has a bad disease.

A samurai could divorce even if he simply did not like his wife, but this was avoided because it would embarrass the samurai who had arranged the marriage. A woman could also arrange a divorce, although it would gtake the form of the samurai divorcing her. The fact that the samurai had to return the betrothal money after a divorce, also often prevented them.
If her background had been strictly checked by a higher ranked samurai, a samurai could have a mistress and, in many cases, this was treated as a marriage. Kidnapping a mistress, although common in fiction, would have been shameful, if not a crime. 
The concept of a woman being a fit companion for war was no longer conceivable, and because of the rise in Neo-Confucian influence and the established marriage market of the Edo Period, the status of the onna-bugeisha diminished significantly. Travel during the Edo Period was demanding and unsettling for female samurai because of imposed restrictions. They always had to be accompanied by a man, and had to possess specific permits, establishing their business and motives. Samurai women were severely harassed by inspection checkpoint officials.
Probably the last great female samurai was Nakano Takeko. In 1868, during the Battle of Aizu in the Boshin War she led an ad hoc corps of 20 female combatants against the onslaught of 20,000 Imperial Japanese Army soldiers, her naginata held high. Nakano received a bullet to the chest and, rather than let the enemy capture her head as a trophy, asked her sister, Yūko, to cut it off and have it buried. It was taken to Hōkai Temple and buried under a pine tree.
“For such a noble tradition.” Robyn said. “It certainly doesn’t explain why men cut in front of me.”
“No, it doesn’t.” I said. “And it may worsen again. The Nippon Kaigi, the largest right-wing organization in Japan, bemoans ‘the rampant spread of gender-free education,’ staunchly opposes the notion that a woman could be emperor (despite the existence of Empress Jingu two millennia ago), or even allowing women to use their maiden names after they get married. In Japan they still use the expression Danson Johi. Men over women.”


    ‘The secret to a happy marriage is this: Treat your spouse all of    
      your life as you did when you first met and there will never be 
      room for discord.’
  Yamamoto Tsunetomo, Hagakure- The Book of the Samurai, 1716