It's the tone that surprises Inigo the most, actually making him look at the other almost immediately after Tidus speaks up.

Not that Tidus never sounds like that. He can be determined in his own way, stubborn in others. But he suddenly takes on the tone so easily even for a sensitive topic like this, and Inigo immediately knows what it means - only confirmed by the words Tidus speaks after it.

".. did your father tell you to quit and give up?" The famous father Tidus spoke of earlier. Inigo manages to hold his gaze as he says it, though his eyes still mostly contain the vulnerability behind the words he spoke earlier.