Selling in Japan first time as a US Seller (Help)

I am a US-based seller who sources out of mainland China, I want to expand to the Japan marketplace and I am wondering what are the common mistakes some of you guys made when trying to enter this marketplace. I am also wondering what are some logistically difficult things you had to work out before sending products to Japan.
I know Amazon has a program called SEND that uses SJL to pick up packages from mainland China and send them to FBA warehouses in Japan for a very small cost. Does anyone have any experience with this? If so, can someone highlight their experience?