Hakyeon was never much of a cat person, Leo knew this. Heck, Hakyeon actually broke out in a rash just by touching the fur. Leo was a cat person though, he loved felines down to his core. He never knew how much he was in love with Hakyeon until he saw how beautiful his heart was. 

Taekwoon says this, because despite it being freezing and the water being deathly cold and Hakyeon is pregnant, he had no hesitation when it came to jumping into a river to save a drowning kitten.