Japan invest on their young and talents and Their development start academically from Basic teams(u 17). At the club level, they are the finalists of the Asian Club Cup almost every year and have the most championships both at the national and club level in Asia. In the past(20 years) Iran's football was ahead of them but now our football level is too far from their level. from my point of view the level of Japanese football is beyond of Asia, and If they were in Europe they would capable to to qualify to World Cup.
Japan also struggle to make as quick a mark as they'd like as they realise that football is so developed they can't really put a Japanese stamp on it immediately.
