Chefs in Japan are incredible at doing non-Japanese food. I haven't had the best croissants in Paris, but croissants I've had in Tokyo are better than the ones I've had in Paris.
In France croissants are available everywhere but you have a very high range coming from high artisan standards to very low industrial products with very basic places in the middle mostly heating stuff rather than doing the whole process.
In Japan i guess there's less available bakeries specialized in things like croissants and they sell it as a high quality product. There's also highly qualified bakers from France that are working in foreign countries.
Too much possibles biases to really judge.
[0] Maison Landemaine 03-5797-7387 https://goo.gl/maps/KsWoBvWk6dcyUfkq8