A source speaking with TechRadar has revealed some interesting details about Grand Theft Auto's past and future. First, the unnamed source told the site that Rockstar Games was considering making a "full" Grand Theft Auto game set in Tokyo and even sent staff to the Japanese city for a research trip.

The trip, which is said to have involved taking pictures and speaking with locals, took place "several years ago," around the time of GTA III and Vice City, the source said. Though Rockstar was reportedly "serious" about making a GTA game set in Tokyo, the idea was scrapped for a couple major reasons.

From the TechRadar report:

"The road system was seen to be problematic and became one reason the idea was canned...Our source added that, as time has gone on, Rockstar has realized the difficulty in moving Grand Theft Auto outside of the USA, where it has firmly embedded itself. There are a number of series staples, from brands to cars, that Rockstar would likely have to change if a future GTA was set somewhere else."

TechRadar also points out that Rockstar parent company filed trademark applications in 2003 for GTA: Tokyo, as well as GTA: Bogota and GTA: Sin City. None of those ever materialized. Trademark applications do not necessarily mean much, as Activision has also trademarked Call of Duty: Space Warfare and Future Warfare, among other things, that never came to light.

The site's source also said "preliminary" work has started on Grand Theft Auto 6. However, a location for the game has not been chosen yet, but, if the source is right, it will probably be in the United States.

Rumors of Rockstar working on a new Grand Theft Auto game are not all that surprising. Take-Two has labeled the franchise "permanent," which basically guarantees new entries in the series are coming. Additionally, former Rockstar boss Leslie Benzies said in the past that Rockstar has "some ideas" for Grand Theft Auto 6. There is a clear business opportunity to make a sixth mainline game, as the latest entry, 2013's Grand Theft Auto V, has shipped more than 60 million copies.

It doesn't sound like Rockstar needs to rush it with the next mainline GTA game, either, as GTA V's money-making multiplayer mode GTA Online continues to be incredibly popular.

We have reached out to Rockstar for comment on the source's claims and will update this post with anything we hear back.