How does Shinji react to the mention of Hatsue’s name? Why?

Mostly through Shinji's perspective, the reader comes face-to-face with the diverting, consuming, life-changing power of first love. Shinji himself is surprised at how he reacts to even the mere mention of Hatsue's name after he first sees her one day at the beach. He wonders if he is sick since he cannot sleep. He is confused and disconcerted at how he cannot seem to shake her from his mind.