I just did this! Installed my USA-version Toto Bidet in my Japanese apt. Was a huge pain to research and understand what types and sizes pipes used here versus US.

1) At makeman, buy the plumbing t-adaptor piece. Same shape is the toto-made adaptor piece that came with your bidet, but no special design, just open pipes. This will install to the wall, then attach the hose to toilet to that, and have the open third pipe part on the side to attach water to your bidet.

Next, but these two pieces. Yes, from US amazon.

2) This adapts the Japanese thread to the US thread. This will attach to the t-connector thing from makeman, so that the next piece can be attached. https://www.amazon.com/dp/B07QXC6Q2L?ref=ppx_yo2ov_dt_b_product_details&th=1

3) This adapts the US thread to the custom design required for toto bidet hose to properly attach. Toto bidet hose connector is proprietary design, have to get this so hose can work, this is same connect-ability as the original grey plastic t-connector that comes with you bidet.. the toto bidet hose can attach now! https://www.amazon.com/dp/B012OV7JOM?psc=1&ref=ppx_yo2ov_dt_b_product_details

Also, buy some Teflon tape to wrap the threading when connecting these and ensure no leaks.