It's that old cliche. Walking through the halls with his attention set entirely on the weathered book in his hands, he doesn't notice as his path crosses a little too closely with hers, and he bumps her.

"Oh! Pardo-" He glances up from his text, mouth hanging open.

"P-pardon me! Sorry!"

How on earth did he not notice her? That armor is huge! If it even is armor, she could be a robot... And then he realizes he's been staring the entire time he's been thinking.