'grassroot' spies like that were unlikely to have existed, even if they did, they won't be more useful than gathering local gossips from a tiny village. personal movements were very limited in ancient times, most people never left their village their whole lives, anyone coming in or going out will be noticed right away. the farmers and fishermen were expected to be self sustained yeah? so they had to work 12 hours a day, and then train spy crafts/martial arts in secret and go out and gather intelligence 5km+ away, where would they even find the time, not to mention that's basically paying the lord for the privilege of working for him. much easier to just bribe someone working in the fortress/samurais households