After the Ferris wheel ride, Dragon didn't have the chance to respond to Seraphina's confession for the reason that she stopped him.
After saying what she wanted to say, Seraphina added, "Ryu, don't. I am a selfish person. So, I only wanted to say what I feel but I don't want to hear yours, just yet." Suddenly, her expression turns firm.
Although he doesn't know her reason, Dragon respected her request that instant. Seraphina then turns back to her usual bright self and diverts their attention back to the view. However, something inside Dragon was bothering him.
Now that they got off the ride, Seraphina noticed his indiscernible mood since her confession. The sole reason she doesn't want to hear Dragon's response was that she might admit everything to him -- including everything about her being a mafia Don.