Alright, I just played through the Kabuki Den demo.
The only differences I noticed between this and the real deal is:
-no saving.
-no sound effect when you climb ladders in the mine.
-different and/or additional sound effect when you open the golden lion statue.
-curser position saving.
-if you don't tap a button to end a text box with an arrow, it eventually clears itself(these last 2 maybe menu options in the full version, but I don't remember them).
-when you select the "Finish/Stop" command at the end of the Kanbie battle, it keeps flipping and you have to use one more regular attack instead to get him to talk.
-when Jyoukou offers you the Demon Sword, he also drops a chest that has some sort of equipment in it(armor?).
-when you leave Jyoukou's mansion, you get a full screen ad for Kabuki Den, with Kabuki spelled in Hiragana, featuring the date and price. You have to reset to get rid of it.
-some of the sprites and or graphics looked a little different colorwise for the mostpart, with a couple portraits that looked like they were later touched up. This could just be from my seeing the game in S-Video for the first time.
-I'm pretty sure that there were one or two other minor (sound effect?)differences.
This is pretty much the same deal as the Tengai Makyo II demo that was on a disc with a Dragon Slayer demo to promote the Super CD format. In that game, the demo also ends after you beat the first boss.