This endpoint is the secure 3D Secure / ACS bridge used by the checkout flow. The HTTPS certificate for acs.tokyotickets.store is installed and valid.
To proxy or hand off an ACS challenge, call this endpoint with a target URL:
https://acs.tokyotickets.store/acs?url=https%3A%2F%2Fexample-bank-acs.com%2Fchallenge