The source of the text is the translation and (probably) adaptation of the book of Samurais. So, the type of source is secondary.
Hagakure was written during the period 1709 – 1716. however, it was not issued until many years afterwards. It is a realistic and sacred guide for a warrior, originated from a collection of commentaries by the samurai, Yamamoto Tsunetomo, former retainer to Nabeshima Mitsushige, the third sovereign of what is now the Saga region in Japan. The book discovers Tsunetomo’s regards on bushido, the warrior principles of the samurai. Hagakure is sometimes regarded to declare that bushido is really the “Way of Dying” or living as though warrior was previously dead, and that a samurai payment must be wishing to die at any instance in order to be true to his lord.
The author of this book of Samurai created it with the aim to leave his own legacy for further generations. As the book describes the life and death of a samurai. While Hagakure is perhaps the best known explanation on bushido, there are those who view Tsunetomo as to some extent of a fanatic, a label he himself would neither refute nor dislike. For instance, his censure of the Forty-seven Ronin is grounded on his estimation that they should not have waited a year to retaliate their lord, but should have tried revenge instantly, even though an instant effort almost certainly would have failed. While most see the achievement of the forty-seven and praise their endurance, Tsunetomo believes that acting instantly is ultimately more significant than whether or not one thrives in attaining the aim.
The context, the book was created in is the following: After Yamamoto’s master died, Tsunetomo himself was prohibited to perform tsuifuku, a retainer’s ceremony self-kill, by an proclamation of the Tokugawa Shogunate. Hagakure may have been written partly in an attempt to outline the role of the samurai in a more nonviolent society. Several sections submit to the “old days”, and entail a hazardous weakening of the samurai class since that period. The Hagakure was written roughly one hundred years after the start of the Tokugawa epoch, a time of comparative peace. With no central campaigns to fight the samurai were changing from a warrior to an managerial class. His work represents one advance to the matter of maintaining military attentiveness and a proper military attitude in a time when neither has much practical application.
Talking on the matter of biases, it is necessary to give the direct quote from the book itself: If one looks at the world when affairs are going smoothly, there are many who go about putting in their appearance, being useful by their wisdom, discrimination and artfulness. However, if the lord should retire or go into seclusion, there are many who will quickly turn their backs on him and ingratiate themselves to the man of the day. Such a thing is unpleasant even to think about. Men of high position, low position, deep wisdom and artfulness all feel that they are the ones who are working righteously, but when it comes to the point of throwing away one’s life for his lord, all get weak in the knees.
Hagakure book gives the clear realization of the realities of life in XVIII century Japan. Those, who are interested in Japanese philosophy will have a great opportunity to study the very essence of it, as samurais are the social stratum, that concentrated everything the best from such spheres as Japanese art, philosophy and literature.