To get the good ending you need to beat every stage at least twice to get all circuits and talk to Merca to turn the circuits into Soul Fragments. Once you have all Soul Fragments you go to the last world and beat it. So to get the normal ending you just need not to get all fragments.
But that doesn't work. Because of a programming error. No matter what you do, you will never get any ending. The text that shows Ai's thoughts are images in the background that come and go when you touch invisble events, but these events are coded to be on the same priority as Ai, so instead of going over them you hit an invisible wall and can never advance, so the game is impossible to beat. For years, I never knew what the problem was and neither did the people coding the game, but that's the problem. So I fixed it, and now here you have the ending.
The transition to the credits in this ending is good, but I'm not showing the credits for the sake of the creators. I know they wrote them willingly and anyone can easily get the game and play it to see the credits, but I don't want to show them myself. If anything changes, I might show the credits in their own video, but all I'll tell you is they're slow. Veeeery sloooow!