Looks like a very cool and promising series, on my first walkthough I met some bugs and managed to complete the game only thanks to them in like half an hour (the boss was pretty hard) and then I took my knowledge and beat it with time of 8:40 I used "first key-piece duplication" bug rushed to get the sword got third key piece from shopkeeper and beat the boss.

bugs I found

"first key-piece duplication" bug where you get it normally and then go to the room below and clip into the wall where you can move by jumping and collect the key (also I have no idea how to get the second key piece bc its on a high platform)

"cyclone gate skip" you need to locate yourself on the right side of the gate opened with cyclone slash and jump towards it then take a step to the right and go down (bc I couldn't understand the puzzle before sword I was trying to clip the wall around the gate but clipped the gate itself)

also I noticed that the big black ghost on the way to the statue doesn't hurt you (and it confused me so much when it hurt me on the boss fight)

"crystal charge skip" during bossfight on second phase when you charge AP and have to fire four flames and kill white ghost so that the rocks explode and you destroy the orb behind them, you can just stand on the right side of the rocks and slash with the sword and the orb breaks

overall it was pretty cool experience and I had fun finding bugs (I also always wished for the game to have a "bug menu" where you can choose some bugs to work or not it would be pretty fun and cool, Im not good at programming so I dunno if thats hard to implement or not )