On blue dragon what class is good for shu?

His main class is SWord Master, but it depends on what level Blue Dragon is in that rank.

For example, if he's a level 32 in Black magic and 14 in SWord Master, most likely he's going to be stronger in the Black Magic class. But certain stats will be lower (such as physical defense) and some will be higher (like magic attack)

Really, Shu is more of a fighter and he doesn't have as much mana points as Kluke or Jiro. I'd set him up as a monk, assasin, or sWord master.

Though if you'd like, you could eqip the Generalist class and have him learn a skill called "Skill +1", which is where he can learn more than just four skills. So if his skills column is full and you have the SWord Master Lv6, you could add that to the list. So that way, he'd still have the four skills from before as well as this one. This is actually pretty useful seeing how you don't have to constantly swap out different skills to equip new ones.