Yes, you should definitely be cautious. While minor surface rust is common and often fixable, structural rust on the chassis is a major red flag. It can weaken the vehicle's frame, making it unsafe in an accident and leading to expensive repairs or a failed inspection.

When searching for reliable second-hand cars in Saitama, Japan, always check the undercarriage. Saitama’s mild climate generally keeps cars in better shape than those from snowy northern regions, but it is still vital to inspect for "scale rust" or holes. A clean chassis ensures long-term safety and value.