This one has me confused. At first I hoped it was an early Japanese machine but the closer I look the more it seems to be a homemade special that just happens to have some Japanese script on the tank.
My overall synopsis of it is that the bike is something of a death trap. A powerful JAP ohv 'dog eared' sports motor with Triumph twin barrel carb, wobbly Triumph 'rocking' front forks, no front brake, belt drive and just a drive rim brake on the rear. It's rather hard to put a date on the bike, the overall spec suggests around 1920 but the engine comes from somewhat later (mid to late twenties).
The gearbox is a Sturmey Archer and the overall appearance very sporting. Having had a look at early Japanese bikes the number plate could just be Japanese but equally it could be British - if it is indeed British it comes from Bradford. The logo on the tank is a mystery but the most likely explanation is that the bike was put together as a special by someone who had a knowledge of Kanji script, perhaps an impecunious student who built their own sporting mount? Putting the tank logo through google translate comes up with 'about three' - maybe it refers to the number of different bike brands in this particular mongrel?