I've heard of this mathematician several times over the years, but have never seen the capabilities and point of view of his calculus-like system actually described. Does anyone know of a more detailed article or book that gives such a description?
One of the books given in the references is actually available in it's entirety [1] and appears to be quite good. Chapter 6 covers Seki, Chapter 7 is about his contemporaries and western influences (or lack there-of), and Chapter 8 is about the 'yenri', which is the Calculus system in question.