There are no runes at all in this game, and no characters from any other suikoden games.
The hero actually talks in this game, which makes a change.
The castle is not that bad, actually. No mini games, but one of the characters has a movie gallery which lets you view all of the animated cut scenes, which are quite nice. You can also get a training hall in the basement which lets you fight summoned monsters of different levels. There is also a character who provides you with jobs and quests, which allow you to recruit new characters.
The 2d hand drawn environments are very pretty but the polygon characters are hideous. All the characters have the same proportions, and instead of having their own personal weapon and fighting style, you can choose different weapons to give every character, so they don't really have their own animations either. It would have been much better if the whole game was done in 2d.