They're bath boosts. So you have to manage to luck out and meet them in the bath while having the appropriate relationship level to obtain their boost.
Tatara can give you Armory or the weapon equivalent(Man at Arms I think?) which boosts the rate your armor or weapons "level up".
Shusui has Appraisal.
Shikimi gives Greed.
Yamato increases the chances of obtianing Mitama.
The 6 combat NPCs each give a bonus that affects their weapon type.
I forget Kikka and Yu's abilities =/
hmm. is there a list/site that has all this abilities listed?
there should be a selection in the menu that allows us to know what's active too!
damn. I thought talking to Yamato before every battle would give me that Mitama bonus... lol that's why I kept doing it (and kept getting Mitamas)... only to release it's all a big lie. lol
But I talk to everyone every time I go back to the Town/HQ... not sure if that affects anything