Well, the name Xbox does not translate well in Japanese. X is canceled or No or Cross. Tho the MSX from Microsoft did well in Japan in the 1980s so they don't just simply reject American companies as Apple is popular there. Xbox consoles do generally have the appearance of a GMC Truck or something. Sell a Ford F150 to someone in Japan. The other problem is the library. Halo and Gears are VERY western. Xbox 360 is the best MS did over there post MSX. Less than 2 million systems. Sleeker design. Got some RPGs like Tales of Vesperia, Blue Dragon, and Lost Odyssey. A lot of Shmups. Some exclusive to Japan. Datings sims and more.  I don't think they tried that hard after that first couple of years. They just sort of gave up and focused entirely on the west with Gears and Halo. MS also was never going to get Monster Hunter,Dragon Quest or Persona aside from s, spinoffs like the Arena or Dancing games. PlayStation and Nintendo are an institution over there anyway. If I were head of Xbox in 2005. I would not put the Xbox logo on the 360 in Japan. Just the 360. (Nintendo used this same marketing with the Wii. It was marketed to older people as Just The Wii, not the Nintendo Wii as Nintendo was video games, Wii was something that didn't sound like a video game) I would have tried to have some RPG on launch day (not Enchanted Arms but something else) and a shmup. DOA4 and RR6. A very Japanese launch lineup. Delayed the launch to Spring or Summer 2006. See if Blue Dragon could launch the first week of November with a big marketing push and still do the Blue Dragon Xbox 360 console special edition box. Then have on the 1st disc both part 1 of the game but a teaser for Lost Odyssey.

People from Japan tend to buy from Japanese companies. Culture alone made it an uphill battle.

Throw in the low support from Japanese devs, that only got worse as time went on, and the subject is hardly even up for debate really.

The XBOne simply had no appeal for the japanese market. Not only there was no confidence in the brand succeeding after the 360, but it also lacked many JRPGs and other more japanese centric titles, was more expensive than the PS4 and the WiiU/Switch, and overall did nothing that the competition couldn't do much better in their eyes.

On top of other reasons mentioned, the name didn't help. Xbox One? Oh so it's the first one? Why would I want to buy that again? I guess 360 is still their newest device and that thing is old now.

Same thing happened to Wii U. Is it a controller? It still has Wii in the name and I don't see a 2 so it must not be a new device.

Most consumers are casually paying attention and get easily confused. Whoever came up with either of these names probably lost their jobs. Xbox Series X is going to bomb as well, I predict, for the same reason. There are going to be a ton of people that have no idea what it is based on the name.

Sony at least makes it easy for consumers to know when there is a new device. And for the record I hate PlayStation, I'm just saying at least they make it easy for their customers.

I think it's because they thought the console looked absurdly large to the Japanese, who are very small people compared to Europeans.

Microsoft, Gen 7: "Well we tried really hard, and invested a lot into reaching Japan and we sold under 1.7m systems."
Microsoft, Gen 8: "Let's not even try this time then."

Because there is not enough reasons for Japanese to buy a X1.

Yep, the 360 sold decent until MS abandoned it in Japan. After the abandonment, the XB1 had 0 effort put forth and was in turn abandoned by Japanese consumers.

From what I remember, MS actually put in effort into the region with 360 (although that support dried up around 2010 and after). If MS could consistently do what they did with 360's early years in Japan, they could probably build up a decent following to warrant launching the system there. I'm sure MS would take almost 2 million consoles sold in Japan compared to 55k they sold this gen

Let's see...
Lack of JRPGs and other types of games that a lot of Japanese players enjoy.
High price
That's pretty much it. Xbox 360 didn't do better percentage-wise in the market than the Xbox did. But the 360 had a way higher amount sold worldwide than the original Xbox, and was able to sell over a million in Japan.
The Xbox One really never had a chance in Japan. The Xbox Series X will be lucky to sell 0.5 million lifetime units in Japan.