Yes, you MUST have a "Temporary Visitor" stamp or sticker in your passport to be eligible for the Japan Rail Pass.

• The Issue with Automated Gates: If you use an automated or facial recognition gate at airport immigration (Narita, Haneda, Kansai, etc.), your passport will not be stamped automatically.
• Required Action: After passing through an automated gate, you must approach a customs/immigration officer and request that they place the "Temporary Visitor" stamp in your passport.
• Consequence: If you do not have this stamp, the JR staff at the exchange counter will be unable to verify your eligibility and will refuse to issue your pass.