I'm just really, really confused at this part. What are you concerned about? If it's the invisible part, I can easily change that. If it's a worry about it being overpowered, well...
Between a Border manipulator, a Time/Space Manipulator, basically-completely-immortal girls and a human shrine Maiden who can wreck the above three I feel like the Netherworld Express should be the LEAST of your worries.
The spellcard system is meant to make sure that those five can compete on(relatively) fair grounds with even Cirno, Kingman