'Genju' means 'We live in maboroshi.'
A 'maboroshi' refers to an image, an illusion, a phantom in the mind, or something that eventually vanishes, but it is something that cannot be put into words.
It means that we should not be attached to things, money, or delusions because we live in an 'maboroshi' that has no substance.
It is a form of training to place oneself in the emptiness of nature and realize the oneness of nature and the self.