Guillotine Bride, Vol. 1 by Daigo Murasaki
Rinne has been sentenced to death. That's where the dragon princess' story should have ended. Instead, she's blown out of the sky en route to her execution and winds up in front of Ryuunosuke. The young boy has no time to be shocked by this wild development because the dragon girl needs him to lend her a handin marriage! For the sake of the world, Ryuunosuke has to marry Rinne and smother her with love because if he fails to keep her in check, the entire human race will probably go extinct...!