These are versions of the game that have been released to the public. There are of course other releases such as pirate copies/compilations and preview/demo copies in which various aspects of the game may be different, some of which may be found listed in the Collectables section.

"Destiny awaits!
Long ago, the warriors of Light defeated Darkness, but in time, the story became just an old legend. For many years, the world was at peace, but eventually, disaster slowly drew near. Thick, mysterious clouds formed overhead, blocking out the sun, but not releasing a drop of rain. The people were tormented by drought for years. Then, monsters began to appear, and people's hearts filled with despair. King Marcel, the ruler of Klantol, feared for his people's welfare. And so, he announced a grand tournament at the colosseum to find a mighty hero that could protect the country and vanquish the wandering monsters.
'Heroes who have inherited the power of Light, save this world from being engulfed in Darkness!"
  from the Shining Soul II box

Sega's Official Shining Soul II mini-site, is located here: sega.jp/shining2/ .

Shining Soul II is a sequel, of sorts, to the original Shining Soul. It is, however, significantly improved in terms of features and in basic gameplay.

If it came to a choice of buying only either Shining Soul or Shining Soul II, this is certainly the one to go for!