The Japanese start with one Squadron of I think 8 Ki-44 Tojos in Canton in Scen#1. But they can't produce any until they are officially researched, you can see them as early prototypes.
What you can do about them? The same thing you can do with every other Japanese Plane type as well, bully them with superior numbers and train up your pilots
On a more serious Note, there is little you can do at the very early game to fight the Zeros, Oscars and the 8 Tojos effectively, don't expect 1:1 Kill Ratios against them. They have a superior Plane and most importantly elite Pilots at the start. The best thing you can do to minimize your losses is to avoid combat against them at the start as much as possible and train up your pilots to more reasonable values. Especially the Skill Def is very important to keep your Planes alive.
After you have trained up your Pilots skills to the 60s you can try to engage the Japanese Fighters, but always try to do this with superior numbers and don't let yourself get dragged into an attritional battle. The Japanese will win every kind of attrition competition in 1942 against you (Ships being the exception here).
Also layer your CAP if they come from very high altitudes, don't try to fight them on high altitudes as your Fighter Planes perform even worse at them. It is generally better to let them first dive onto you and then let your higher Layer of Fighters dive onto the Japanese Fighter afterward, as they are now on a lower Altitude. Your Fighter are more durable and can survive the initial dive, especially if you have trained your Def Skill.
But as I said, don't expect 1:1 Kill Ratios this early on, only engage if you are in an advantage and fall back if you aren't.
And once you kill their starting elite pilots, fighting them becomes easier as well.
Yeah, I pretty much avoided them after I encountered them a couple of times. They shot down 5 or 6 planes of the AVG in China, however, which was a bit annoying...