From the Introduction:

This is a work in progress and therefore incomplete, based on an Oriental supplement that we originally wrote using the Warhammer Fantasy Roleplay rules.

Our intention with Tetsubo now is to convert it to the Fabled Lands RPG (itself a work in progress) and modify the setting to Akatsurai, the easternmost country of the Fabled Lands. As well as fully revising the background, we will reinstate the missing sections (marked here in red) and add a scenario section.

The new work will then be released as the FL RPG and the first of twelve planned sourcebooks. And yes, we are hoping to do that this lifetime.

Other Tetsubo material can be ordered from Robert Rees here.

User summary:

A formal announcement of TETSUBŌ Grim & Perilous RPG was made by Daniel D. Fox, creator of ZWEIHÄNDER Grim & Perilous RPG on October 8, 2018. TETSUBŌ will be redesigned and released by Grim & Perilous Studios in 2019. This effort formally was cancelled in March 2020.