What is an Honor Duel
The nature of an honor duel is to force those who act in an insulting fashion, whether they know it or not, to demonstrate their personal honor and present that they truly meant no harm. Especially considering that the duel itself leaves it up to the winner whether to spare a person's life or to take their life. It is one of the few times where it is considered acceptable to kill another living person. Even in war, it is considered dishonorable to intentionally kill your enemy as honor dictates that a defeated foe is to return home, for further participation only brings greater and greater dishonor to you, and your comrades.
In an honor duel, to demonstrate that scale of trust in letting another have that much power over each other's life is ultimately an act of balancing the scales between all economic, social, and religious classes.
What you do to win an honor duel is ultimately up to the combatants. Both sides are expected to be transparent on their abilities and to dictate whether or not they are going to end their duel partner's life. Ironically, this is considered one of the few times it is acceptable to lie on every count, as the ability to mince words and create belief is considered a skill for survival and victory.
The end result of that duel is the opinion of the public that matters afterward, as your conduct will inform the public if you are someone that they should treat with skepticism or trust.
Obligations to an Honor Duel
The lowest of slaves can challenge the Shogun himself to an Honor Duel in which the Shogun can accept. This is enforced by the will of the Fae to ensure that no man is unequal and faces a shared peril and appreciation for the short life that they are gifted.
It is considered a faux pas, but not dishonorable, for someone of a higher class to challenge someone of a lower class. But it is done if an insult is performed. This includes insulting a person's greater charge. Eg, if you insult the Shogun, you insult your Daimyo. If you insult your Daimyo, you insult your village council. And so on.
If I Refuse an Honor Duel?
There are some sociopaths that use Honor Duels as a form of killing others, which generally results in the Order of Chowa to intervene and slay the individual by any means necessary. In such contexts, it is regarded as forgivable despite the hit to a person's honor. It is generally considered severely dishonorable to challenge a person more than once without cause, so such sociopaths generally are forced to move on from small population centers quickly before Chowa catches up with them.
But to refuse an Honor Duel without cause is generally forgivable. If it is communicated that they have a cause, and are explicit to the cause, you may ask for forgiveness, but it will be considered an Honor Duel with cause.
To refuse an Honor Duel with cause is considered poor form and highly dishonorable. Many people, when they become aware of your refusal, will regard you as "dead" in spirit, and often will do as much as they can to not recognize you until you have honored the Honor Duel.
If an Honor Duel is requested via any form other than directly facing a person, looking them eye to eye, standing on two feet, it is considered invalid and in poor form, but not dishonorable.
Females are not expected to offer or accept any Honor Duel but have the freedom to choose to do so if they please.