Dogen writings on reality and death What is meant by body mind and the world is born simultaneously ...Buddha nature will never break apart. Do we die or is life eternal.
Buddha-Nature refers to the mind free from suffering or free from 'self-views'. Buddha-Nature is the pristine purity of clear-light-radiant mind.

'Death' does not occur to Buddha-Nature because Buddha-Nature does not have any ideas, thoughts or views of 'self'. 

Try to realise the worries, fears &amp; traumas about 'death' are all related to beliefs in 'self'.

When there is no belief in 'self', both internally &amp; externally, there is no 'death'. 

This is called 'The Deathless'. 


  To study the Buddha Way is to study the self. To study the self is to forget the self. To forget the self is to be actualized by myriad
  things. When actualized by myriad things, your body and mind as well
  as the bodies and minds of others drop away. No trace of enlightenment
  remains, and this no-trace continues endlessly.
  
  Dogen




As for 'body &amp; mind', these are just elements of nature that form the natural world. Dogen, above, emphasises dropping way the false idea that various bodies &amp; minds are 'myself' &amp; 'other selves'.