Alt-Onin War - A Word on Tropes

It looks like there is some confusion about what this era of Japanese history looks like. Most of the tropes you are familiar with, including the following, are actually relatively late in history. 

• Samurai following a strict code called Bushido
• Samurai with two swords, and nobody else allowed to be armed
• Samurai with shaved heads and the Chonmage topknot
• The streets filled with scruffy ronin
• A powerful shogunate calling all the shots
• Kabuki theater

All of these are products of the Tokugawa Era (1600-1868), which would be more like the 1600's-1800's of Europe. Think of the Three Musketeers, powdered wigs, smallswords and rapiers, and that's what all of that stuff is more like. Same era, other side of the world.

Our campaign setting is a medieval setting, with events cribbed from the 1300's-1400's. Japan was a rougher, more divided place, and the samurai's code of honor was more loosely defined. The ethics and morals were very similar, but "proper behavior" and etiquette were not nearly as rigid. The things you think of as "samurai behavior" actually evolved during this era. 

Wikipedia says the following: 

Muromachi-Azuchi (1336–1603)

During the Muromachi period (1336–1573) the way of the warrior began to refine by inserting in their daily activities, alongside martial training, Zen meditation, painting (monochrome style), ikebana, the tea ceremony, poetry such as the death poem (written by samurai before suicidal missions or battles)[48] and literature.[8]

Carl Steenstrup noted that 13th- and 14th-century writings (gunki monogatari) "portrayed the bushi in their natural element, war, eulogizing such virtues as reckless bravery, fierce family pride, and selfless, at times senseless devotion of master and man".[49]

Every farmer was basically also a warrior until Hideyoshi confiscated weapons through a nation-wide "sword-hunt" in 1588. Every ashigaru had his first lessons on the mentality of war from the biwa hōshi. On the other hand, the Heike recitations also propagated civic virtues: loyalty, steadfastness in adversity, and pride of family honor.

— Carl Steenstrup[49]

Daimyo Katō Kiyomasa

The sayings of Sengoku-period retainers and warlords such as Katō Kiyomasa (1562–1611) and Nabeshima Naoshige were generally recorded or passed down to posterity around the turn of the 16th century when Japan had entered a period of relative peace. In a handbook addressed to "all samurai, regardless of rank", Katō states:

"If a man does not investigate into the matter of bushidō daily, it will be difficult for him to die a brave and manly death. Thus, it is essential to engrave this business of the warrior into one's mind well."

— Katō Kiyomasa"[50]

Katō was a ferocious warrior who banned even recitation of poetry, stating:

"One should put forth great effort in matters of learning. One should read books concerning military matters, and direct his attention exclusively to the virtues of loyalty and filial piety....Having been born into the house of a warrior, one's intentions should be to grasp the long and the short swords and to die."

— Katō Kiyomasa[50][clarification needed]

Nabeshima Naoshige (1538 – 1618) says similarly, that it is shameful for any man to die without having risked his life in battle, regardless of rank, and that "bushidō is in being crazy to die. Fifty or more could not kill one such a man". However, Naoshige also suggests that "everyone should personally know exertion as it is known in the lower classes".[50]

By the mid-16th century, several of Japan's most powerful warlords began to vie for supremacy over territories amidst the Kyoto government's waning power. With Kyoto's capture by the warlord Oda Nobunaga in 1573, the Muromachi period concluded.[23]

In 1551 CE, one of the first western people to visit Japan was the Roman Catholic missionary Francis Xavier. The description of Francis shows that honor, weaponry and warfare were valued of utmost importance in Japanese culture.[35]

The Japanese are very ambitious of honors and distinctions, and think themselves superior to all nations in military glory and valor. They prize and honor all that has to do with war, and all such things, and there is nothing of which they are so proud as of weapons adorned with gold and silver. They always wear swords and daggers both in and out of the house, and when they go to sleep they hang them at the bed's head. In short, they value arms more than any people I have ever seen. They are excellent archers, and usually fight on foot, though there is no lack of horses in the country. They are very polite to each other, but not to foreigners, whom they utterly despise. They spend their means on arms, bodily adornment, and on a number of attendants, and do not in the least care to save money. They are, in short, a very warlike people, and engaged in continual wars among themselves; the most powerful in arms bearing the most extensive sway. They have all one sovereign, although for one hundred and fifty years past the princes have ceased to obey him, and this is the cause of their perpetual feuds.[51][52]

The practice of decapitating and collecting enemy heads is an example of honor in samurai culture.[53][54] The decapitated heads were shown to a general as evidence that they killed wanted opponents and to collect rewards.[54] More heads meant higher prestige, honor and rewards.[54] A beautification ritual of the decapitated heads called Ohaguro was performed.[55][53] Prestigious heads were arranged on a table and presented in front of the warriors.[53][54] All heads were identified and marked to prevent mistakes.[54] The guards were left and right of the general and cited spells to transfix demonic spirits of the enemy.[54] Then a samurai said his own name, lifted a box to show and describe the decapitated head.[54] The general inspected the trophy heads while holding a fan so that the dead could not recognize his face.[54] If the claimed head was correct then the samurai received a payment otherwise he was dismissed.[54][53]

Despite the war-torn culmination of this era and the birth of the Edo period, Samurai codes of conduct continued to extend beyond the realms of warfare. Forms of Bushido-related Zen Buddhism and Confucianism also emerged during this period.[56] A Samurai adhering to Bushido-like codes was expected to live a just and ethical social life; honoring the practices of the gentry in the absence of military campaigns.[56]