Depends where and when you want to go. Tokyo is the cheapest destination, Osaka the most expensive. Spring and autumn the most expensive times to fly. I travel to Japan several times a year, I always look at every travel and comparison website and go with the cheapest there. You really need to decide when you want to go first. Indirect flights are a pain, a 12 hour flight can become a 24 hour one. Remember you always need a return ticket when entering Japan....