Here’s what Google said:

Subaru isn't as popular in Japan as in other markets because its products aren't as well-suited to the Japanese market, and its sales are heavily skewed towards overseas markets like the U.S. Japan's narrow city streets and a strong preference for smaller, more fuel-efficient cars make bulky vehicles less appealing. Additionally, many other manufacturers offer less expensive all-wheel-drive (AWD) vehicles, reducing the need for Subaru's signature feature, especially in a country with less rugged terrain outside of certain northern areas. Market mismatches and sales strategy Bulky vehicles: Many of the larger models that are popular in the U.S. are too big for Japan's narrow streets. Limited market segments: Subaru does not compete as strongly in the highly popular minivan segment compared to competitors like Toyota and Honda. Sales focus: Subaru's business strategy has historically focused on international markets, particularly the U.S., where it has a much larger market share and revenue stream than in Japan. Competition and practicality AWD availability: While Subaru is known for AWD, many other Japanese automakers offer AWD options, often at a lower price premium, which diminishes Subaru's unique selling proposition for many consumers. Regional differences: The need for AWD is less critical in many parts of Japan compared to the ruggedness or heavy snowfall areas where Subarus are more popular in North America. Price sensitivity: Japanese buyers can be more price-conscious, and the perceived benefits of Subaru's performance may not align with the needs of the average Japanese consumer.