I will add to this later, but here are some starting basics.

Izu Village

You start off in Izu village and the first thing you need to do is talk to the Village elder Gisaku (he’s an old man in white who’s bent over with age) he can be found walking towards to village inn so if you don’t see him right away go there when you are ready. It’s definitely worth visiting the armor seller who has an open market stall near a section of broken wall. Its mostly shoddy grade stuff, but the helmets are definitely worth buying. Inside the village inn the bar keep sells some miscellaneous items including thief back packs. Once you have spoken to the Gisaku and accepted the mission you will be approached by a mysterious Ronin Ryunosuke (save before you speak to him, ditto most characters) and accept his help.