The following image, which is sourced from David Cenciotti of The Aviationist (in turn claimed to be from "Chinese Internet," the catchall usual suspects of anonymous aero-defense news) purports to be a manned flying prototype of the Mitsubishi ATD-X, a stealth demonstrator leading the way for Japan's effort to build its own F-22 or F-35-like Stealth Fighter.
Japan's Air Self-Defense Force is an ideal candidate for stealth fighters and consequently the government feels highly vested in fielding a fleet not only with stealth capability but capability (stealth and otherwise) near or at parity with the U.S. Because U.S. Congress has blocked any and all exports of the F-22 to anybody, including our closest allies, it's become in the best interest for the Japanese to develop their own indigenous stealth fighter production capability.
In many ways, the defense situation of Japan isn't much different from that of Canada, which is currently reviewing a controversial purchase of F-35 stealth fighters. Ideally, a fighter for either nation must have long range and twin-engine redundancy; although the tightly packed and population-dense nation of Japan lacks the sheer land mass of Canada, its extensive coastlines and over-water Exclusive Economic Zones (EEZs) mean very long and exhaustive fighter patrols over open ocean where rescue is dependent on emergency flotation equipment and rations that must last until an allied vessel or helicopter arrives. Also like Canada, the mission profile JASDF fighters typically undertake (especially their anti-ship strike fighters) leave them more vulnerable to bird strikes than what USAF fighters typically experience, especially along the coast (the JASDF's current principal strike fighter, the F-16 derived F-2, has a strengthened wind screen to better resist bird strikes). Unlike Canada, Japan's geographic proximity to North Korea, Russia and especially the People's Republic of China means there's a much greater chance of Japan being involved in an actual shooting war - and very close, if not directly over, their own territory no less. All three countries have some pretty big beef to pick with Japan over WWII - yes, nearly 70 years after that conflict ended. In the case of Russia, they argue that the Kuril Islands, which are in extremely close proximity to Hokkaido Island, rightfully belong to them as what should be recognized by treaty and war reparations. As Putin orders increased frequency of "bomber probing" into American and NATO airspace, his nuclear-capable bombers are doing the same over Japanese territory. The Chinese, meanwhile, also claim a number of territorial and EEZ-related disputes with Japan. And like the Russians, the Chinese also feel emboldened to make grandiose overtures of a military nature such as military exercises near strategically important reefs claimed by the Philippines. With a history of military dictatorships lead by mad men (and not the 60s marketing executive types either, but ones with nuclear weapons) North Korea is a potentially destabilizing wild card and a rational and diplomatically-negotiable motivation to kick off a shooting war is not necessarily needed for "Dear Leader" Kim-jong Un.
This means that, unlike Canada, the question for Japan is whether or not the F-35 represents too little capability instead of not enough. In either case, Japan has committed to the F-35 program, which many feel is enough of a significant edge over potential adversaries (especially compared to North Korea and their extremely antiquated and short-ranged air fleet). However, the same fiscal problems that have plagued Canada's F-35 purchase (and the program as a whole) are forcing Japan's legislative Diet to re-examine the F-35 program as well. Japan also has economic interests in indigenous fighter development - it's no secret that a major motivation of Japan's postwar weapons development relates to jobs programs (which many feel is a major factor in their disproportionate and ballooning costs compared to Western defense programs, even with the F-35 included) and a Japanese stealth fighter in the F-35 class would likely be highly attractive in the export market, something Japanese defense firms are also highly interested in.
So it's only surprising if Japan were to suddenly decide to completely suspend stealth fighter development. At the very least, it would give them an "insurance" program if the F-35 program goes belly-up or otherwise becomes unfeasible for their defense needs; if it develops into a twin-engine medium or large fighter closer to the F-22 class, it would give them a valuable "high" component to the F-35's "low" mix with presumably high acceleration rates and a large weapons bay for quick interception of enemy nuclear bombers as well as a potential and very useful secondary anti-ship capability.