Karatedo is a Japanese martial art.
The martial art is based on the spirit called bushido.(Throughout the history of Bushido, religions such as Buddhism, Taoism, Confucianism, and Japanese Shinto, were incorporated.)
The reason for the “do” attached to the word “karate” is to show that karate and bushido are integrated - as in the common saying “Shingi ittai,” meaning that spirit and body/technique are together.
So anyone who practices karate, especially those in higher ranks, must learn the development of spirit, together with techniques. We have Dojokun for that purpose. Bushido means to be conscious about justice, to cleanse one’s heart and use the purified heart as guidance for one’s actions.
Bushido is not an art of the form, but an art of the heart and actions.
Bushido thus makes people sensitive to shame. Shame of lying, shame of deceiving, shame of stealing, shame of being dishonorable, and the list continues, but these are actions shameful as a person.
Karatedo is said to start and end with rei.
Sit in seiza position with hands on the floor you give a saiko-rei to your master. You give the most respectful bow because the master has a higher character, endured blood-shed hard training for many years, and as a result, earned sublime karate techniques, and that the master is worthy of the highest respect.
The rei is also a reflection of your cleansed heart.

It is unjust, however, for someone to make people kneel down in front of him/her when the standing person doesn’t learn the essence of karate, doesn’t acquire skills, lies about dan for higher ranks and is not even certified. To be not ashamed of the lying and deceiving go against the bushido spirit, hence the karate spirit, and such a person is not worthy being called a karateka.
Bushido is the philosophy and morality of Bushi - it can even be said that it is a commandment.
Through living with Master Asai and the many books I’ve read, I summarized bushido like the following.

The most strict of bushido is the “gi” (right principle.)
For Bushi, unfair actions and wrongful act are considered the most shameful.
Bushido encourages courage, but real courage is not the same as combative courage. It’s courage to be able to be calm at all times. Therefore courage and calm are two sides of the same coin. Bushi should be equipped with moralistic courage, tenacity, and be valiant and undaunted. Those who give in to emotion and act immorally forceful are called “brute courage” and “lowly man’s courage.” There is a saying in China that says: “the bravest of men always looks weak, and the weakest of men always looks valiant.” In bushido, a bushi is expected to have kindness called “bushi no nasake (bushi’s mercy).” Benevolence towards the weak, the lesser, and the lost is considered befitting to bushi.
For that reason, the winner of bujutsu, martial arts, does not show fist pumps, to show benevolence and respect to the lost contender.

Bushi, or fighters, are to develop a refined heart instead of uncouth behaviour. This is said to be achieved through education or developing culture, so bushido is considered an eternal learning process.
The benevolent heart, the refined actions, the kind feeling, and the humanity and respect for other people’s pain are all a beginning of rei.
Bushido placed the greatest importance on rei, and hence even if a bushi wins a battle, he is considered flippant if he did not show the rei spirit. Even on a battlefield, they had the heart to show respect towards the enemies.
Bushido also stresses the need to overcome cowardice and to not betray honor.
Bushi trained with simple clothes and food, and detested ostentatious display (superficial beauty) the most.
Because a bushi sees money as something sordid, a bushi would rather lose than to take profit and taint the reputation, the act of gaining monetary profit by deceiving someone was considered the worst shame.
Also, in bushido that values honor the most the royalty towards the nation binds bushi to live with the nation and to die with nation. For that reason, to bring dishonor to the name of the nation is the worst, most shameful act.

I mentioned earlier that Dojokun are not taught enough and they seem to be just words on posters, but there are still many karateka who understand bushido and karatedo spirits, read and study about them, as well as try to practice the spirits. Anyone who taints the reputation of these people and karatedo itself should be sham and held accountable.

Budo is an abbreviation for “Butoku Koui (the moral act of a samurai”).

According to an ancient Chinese philosopher Laozi, "There are three treasures that I hold, one is Ji (慈, mercy), two is Ken (倹, grace), and three is Shizen (自然, nature)."

Ji is self-reliant, brave, and philanthropic.

Ken is labor, justice, and unity.

Respecting and obeying nature makes a good heart and credible words and deeds.

Three Encouragement and Six Punishments.

First Encouragement: Study hard.

Second Encouragement: See justice and be courageous.

Third Encouragement: Love your nation and protect its people.

First Chastisement: Neglect discipline and training.

Second Chastisement: Flatter superiors and torment inferiors.

Third Chastisement: See advantage and forget righteousness.

Fourth Chastisement: Become disloyal and disrespectful.

Fifth Chastisement: Deceive mentors and humiliate ancestors.

Six Chastisement: Betray and seek profit.

The above is the traditional Butoku.

Modern Butoku is intertwined with traditional Butoku, which states treat people with big heart and manners, do not harm people with “bu (martial)”, do not "torment the weak with your strength", and maintain the virtue to help people. It is said that we will make the greatest contribution to society by admiring the old, loving the young, honoring mentors, respecting morality, and developing both literary and military arts with a strong will of Ji (charity), Yu (courage), and Chi (wisdom).