54. Find the physical location of the border, and prop up a table against it. Bang your head on it to get a sore.
Using the saw, cut the table in half. The two halves make a whole.
Climb through the hole to Gensokyo. However, without spellcards you're in danger, so you'll probably want to get to the human village or shrine quickly. Scream for help until your throat is hoarse.
If a malevolent youkai appears before help arrives, no biggie, just jump on the horse and ride off.