Where is the sudden love between Citra and Rowan coming from? (BOOK 1)

Okay. Okay. I'm almost halfway through the first book. I started yesterday. I love it.

But.

There hasn't been ANYTHING between Citra and Rowan until I suddenly come across:

'Rowan wanted to kiss her. There was no denying that anymore. He had suppressed the urge for weeks because it would not be tolerated by the scythe. But Faraday wasn't here, and the turmoil they had both been hurled into had washed all bets off the table. Then, to his surprise, she suddenly lurched forward and kissed him, catching him completely off guard.'

Don't get me wrong, I love the book. But it feels very random. What do you think?