It's not "Kingdom Hearts", but it's still really good.
If you have a thing for RPGs, this is worth a look. The best thing I like about this game is how creatively strange this game is. You take on the role of a treasure hunter named Rumble (or any name of your choosing) who comes across a weird, big-eared, pig-like creature with the world's longest name (which is eventually changed thanks to you) as you set out into other peoples' dreams in order to help clean up the pig's mess caused by the havoc that he unleashed. That's strange enough, but just wait until you get to the levels themselves.
The strange worlds you visit all reflect the personalities of whom you meet. For example, there is another treasure hunter on your tail really loves money, so naturally her dream is made of gold, jewels, and money bags. All of the levels are very creative and have a unique atmosphere to them. There are a total of eight worlds to go through and it shouldn't take you terribly long to complete the game, unless you wish to get a hundred percent on everything. Along the way you'll come across a sheep, who serves as your source of knowledge for combat, the worlds, etc. All of the other characters you meet are pretty likable and have their own distinct personalities.
The combat in the game is very much like "The Legend of Zelda: Ocarina of Time", which is by no means a bad thing. During combat you are able to carry two weapons at a time. These weapons are known as the Holy Instruments. The weapons are actually orbs that you obtain throughout the game and can only be used in the dream worlds. Your weapons range from a spear, to a crossbow, to a sword, and much more. With a separate button you can activate your shield. As long as you're familiar with the usual Zelda formula you will do just fine in combat. Actually, most of the combat and bosses you face are easy to beat, so you shouldn't have too much trouble. When you're not in combat you are solving puzzles and doing a bit of platforming, which isn't all that difficult.
Graphically it is a very colorful and overall pretty good-looking game, especially for being an early title on the PS2. The game's art direction is even better, bringing a sort of Manga-like appearance to it. The environments and character models all look great. Equally as good is the game's sound design. Some of the music tracks are questionable, but overall they fit the game nicely. There is no voice acting to be found in this game, so the game's dialogue is displayed as word balloons like you would find in a Manga or comic book. The characters however, like Ocarina of Time, make occasional grunts, cheers, yells, etc.
The game does have some flaws to deal with. As I said before the game is pretty easy to beat and you can basically finish the game in around 10-15 hours. Some of the music tracks can get on your nerves, especially when having to hear them over and over. Also, Tumble, while not a terrible character, has a very annoying voice that you will definitely get sick of pretty quickly.
To sum things up:
PROS:
-Colorful and smooth graphics that look pretty good for being an early PS2 title.
-Good art direction
-Likable characters
-Controls well
-Nice weapons
-Some music is nice
-Surprisingly good story
-Works like Zelda 64
-Dream levels are pretty creative
-While not particularly hard to defeat, bosses are unique
CONS:
-Pretty easy.
-Some music gets on your nerves
-Tumble's (the pig thing) voice gets irritating pretty quickly
-Shorter than other RPGs I'm used to
Overall, while "Dual Hearts" is pretty easy to beat through and it doesn't really revolutionize the genre in any way, it is certainly creative and I recommend it as a weekend rental to see if you would want to go further into it. The creative dream settings and quirky characters are, to me, the game's strongest points here and anyone with an appreciation for that should like this game.