I totally agree with you. Si Yu is the most likeable out of all the characters. But he feels more like a younger brother for ZX, they don't really match.
And I sort of got impatient after watching TVB episode 32 so I went and skimmed through the edited China version. Why does Jack kiss ZX's coworker?! I thought Jack was... That totally doesn't make sense and is so out of place. ~_~