Short answer: From that list, Satori is latest.
Long answer: In order of appearance, Kokoro shows up very early on, and Byakuren isn't too long after. Iku and Komachi can be found at the same location about a third of the way through the game. Suika can be found about halfway through the game, and Satori comes shortly after.
In terms of rarity, Komachi and Satori are very common for their areas, and Iku and Suika are fairly common. Kokoro and Byakuren are pretty rare, though they're not the hardest to find (Sariel...). If you're willing to spend a bit of time just walking around you can find all of them easily enough. Byakuren also shows up later a lot more frequently, but that's almost at the end of the game.
