How could i unlock the two last characters?

Just wanted to say I absolutely adore this game's soundtrack. Much respect and appreciation to Gyrowolf! I've already bought it on Steam, since that seems to be the only option currently... is there any chance of it being released on Bandcamp, or added to streaming services like Tidal or Spotify? Maybe a YouTube playlist? Thank you for any information you may have about this....

what s engine of this game (if any)?

I tried it on 2 computers. Both with Windows 10 and a good nvidia card. The Logo of the company shows up, but after that it shut down. Any ideas?

Title. I'm down for the craziest challenges, but you gotta throw a bone to the player here. Getting S rank on Arcade mode is extremely tedious, especially since you're expected to flawlessly pass through an episode without taking damage in one attempt - without being able to restart it. Was going to put some more time into this game, but I might just drop it alltogether if this is going to turn into an unreasonable grind....