Kokudachi (spiritual practice of eating no grain) is one of Buddhism "gyo" (spiritual practices). It refers to carrying out the spiritual practice of eating no grain.
It is also known as 'mokujikikai,' or 'dangokugyo.'
In particular, it refers carrying out a spiritual practice while eating no gokoku (five kinds of grain) and jukkoku (ten kinds of grain).
Named after gokoku and jukkoku, it is sometimes referred to as 'gokokudachi,' or 'jukkokudachi.'
Based on the assumption that grain is a secular produce marred by humans' profanity, this gyo encourages Buddhist practitioners to have no grain to purify their body and soul. Because many practitioners were ascetic Buddhist monks, kokudachi takes the form of 'kugyo' (penance). It is said that practitioners ate mainly nuts and herbal roots instead of grain, but specific procedures have not been established because there are many beliefs as to what gokoku or jukkoku actually represent. Therefore, the hardness of practice varies depending on types of grain that practitioners refrained from eating.
Also, kokudachi is the first step of a series of spiritual practices to become a Sokushinbutsu (Buddhist monks or priests who allegedly caused their own deaths in a way that resulted in their being mummified), the procedures called 'Nyujo.'
Persons who went through kokudachi were called 'kokudachi no hijiri' (highly virtuous monk who has trained without eating grain) in the ancient period and 'jukkoku no hijiri,' or 'mokujiki' after the medieval period.
Sometimes, they are referred to as 'jukkoku.'
They are also known as 'mokujiki shonin' (saint who practiced mokujikikai) because they went through mokujikikai. After the late medieval period, many of those practiced kokudachi played an active role as a Kanjin Hijiri (fund-raising Buddhist monks).
Incidentally, in Taoism, a similar practice called 'dangoku, or hekikoku' (practitioners eat no grain) is observed, but this practice is closer to a fast.