I struggled for a while with Grassblades - it was difficult to pick a title that didn't feel pretentious or that spoiled the entire story. It spent a LOT of time being named "Masahiro-verse" (as in main character's name+[uni]verse) while I tinkered with possible titles. I still have the scribbled notes somewhere, page upon page of suggestions and ideas where none of them fit quite right.
I started getting a bit closer to where I wanted to be when I remembered that I always liked the titles of Lian Hearn's Tales of the Otori-novels - specifically Grass for His Pillow - and Kim Stanley Robinson's Years of Rice and Salt. I wanted something that felt similar to that, but at the same time, it needed to fit the story and not give the whole thing away from the start.
So after MUCH tinkering and changing my mind, I finally settled on "Grassblades", because it reminded me a bit of Grass for His Pillow which is a lovely title - and partly because the "blades" bit of the title is a wink to the fact that Masahiro's got a sword. XD
Basically, I started looking at themes that fit my story (nature, grass, something to do with swords, etc., etc.) and then just tinkered with it till I got it right.