As someone mentioned, pay a bit more and buy in a “real” bicycle shop nearby (avoid stores like Aeon, that also sell and service e-bikes but have revolving personnel that ist not necessarily good at their jobs). Thus you also get quite a bit of basic maintenance for free.
My experience is only with the Mamachari type though, but have used it also for a 60 km a day bike tour of three days, worked fine but less powerful than the one my friend used (probably Trek, not sure how easy it is to get service for those).
The three big ones Bridgestone, Yamaha and Panasonic are all very good when you use it within 20 km per day.
Most people here cover much smaller distances, (to the station, the shops, the Kindergarten etc) so you need to be aware that battery life will be much shorter if you use it a lot, also uphill rides drain the battery quite a bit - in the short and long term. A new battery costs around 40,000 Yen.
Make sure to get a bike with a strong battery. My recent one only has 9.4 Ah and I cannot get up our steepest hill (very steep) with it.
The newer ones have a battery recharge function when you go downhill, but I did not notice a big difference compared to the non-charging bikes.
My recent one is a stainless Bridgestone - with a non-iron chain, which looks more like a flat band, no maintenance needed so far (3 y 9 m). I average 15 km a day, more on weekends and could not live without it in our very hilly area (and with my age
).
Also, e-bikes don’t last forever, my first one gave up after about 10 years, but at that time I still had a child in the backseat and going uphill was probably too much strain on the motor….
Only concern: If you are tall with long limbs, they may be too small for you, maybe there are custom-made options.
Good luck, you won’t regret it.