The main Buddhist sect in Japan is Jodo Shinshu which was almost outlawed for anti nomianism

My understanding is that the Japanese are rather keen on following (or adopting) religious rites without being believers. A modern Japanese person may have a Shinto coming-of-age ceremony, marry at Christian church, and have a Buddhist funeral. All without really being Shinto, Christian or Buddhist in any meaningful sense of the word. In fact, I would argue this superficial syncretism happens precisely because of their lack of belief in any of it.

Sure, if you look for them you will find some devout Japanese, but they are very much in the minority. In every practical sense, the Japanese are exceptionally secular compared to e.g. the US.