Update - The official trailer has now been released and added to the story below, plus here are some details translated by duckroll of NeoGAF:
The game structure is probably going to be like Final Fantasy XII: Revenant Wings. It certainly sounds that way. The game will feature over 130 missions, and is entirely mission-based. You control a single character out of seven possible heroes, and in the multi-player mode up to four players can tackle a mission together as different characters. There are main story missions as well as free missions that are optional
it looks like you can play any mission you've already unlocked.
Original Story - Square Enix has confirmed what many had already presumed - Blood of Bahamut is indeed a new RPG set to hit the DS exclusively in 2009, with the game's logo and name hinting towards a potential link between this new title and the Japan-only release Bahamut Lagoon from the SNES. There will be two lead protagonists in the new DS outing, one called 'Ibuki' and the other 'Yui'. Both characters live in a fortified city built on the back of a giant who sometimes wakes up, normally during enemy attacks. This leads to the heroes having to fight and defend their city with their lives. Blood of Bahamut will feature a co-operative multiplayer mode that caters for up to four players using local wireless, as opposed to online Wi-Fi. This comes as somewhat of a disappointment for fans seeing Final Fantasy Crystal Chronicles: Echoes of Time's splendid-looking online multiplayer mode, however details are not currently set in stone, with the game set to be presented at the Jump Festa expo that takes place in Japan at the end of this year.
Elsewhere in the world of Square Enix, it has been revealed that the company has released a full remake of Hanjuku Hero, the original 1988 NES classic RPG that sadly never made it to the West. The closest the Western world has ever been to receiving a Hanjuku Hero game is with the DS iteration, know here as 'Egg Monster Hero', which actually had an English demo version made to show it off at the first E3 the DS was shown off at. For reasons unknown it was dropped for release, despite selling a healthy 100,000 units in Japan. However, who knows, perhaps this mobile phone remake of the first game, which is even being supervised by the original staff (Takashi Tokita, Kazuhiko Aoki and Nobuo Uematsu), will do what Front Mission 2089: Border of Madness did, and eventually leap from mobile format to DS. Or it might even take the path that many believe Final Fantasy IV: The After will be taking - a WiiWare release in the Western world.
But would you like to see Ganso Hanjuku Hero, complete with its complete overhaul of the gameplay system, graphics and interface, as well as its newly re-balanced combat? What a better way to celebrate the series' 20th anniversary than having the very first game finally released in the West! For now, though, the game is only available on DoCoMo imode phones in Japan for the ridiculously cheap cost of just 525yen (roughly £3.60!).