The one without the grommets definitely looks like silk....The other one has a looser weave and appears to have some information on the header....I would guess that's either cotton or an artificial material....Bodes
Would like to see more pics of the handwriting in the booklet if possible, looks like late war booklet. Might be able to let you know where it was captured with the unit information inside, if present.
The printed entries at the front are imperial rescripts from past emperors; for the soldier to do his duty, etc. There should be one other page that is divided up into printed brackets. That should be able to give the unit information needed for a better ID ( I have attached an example pic below). I imagine at this time, the individual who owned this booklet was probably an older veteran who received a new issue booklet and attended the mandatory one year rollcalls in Japan during the war.