He liked him. It clicked. It wasn’t for pity. It was just out of curiosity to be in a relationship. However, before you jump into thinking that Gon is blind… He’s not. It’s ironic to recognize that Killua is having deeply romantic feelings towards the other more often than, even the fact that Gon is more open and expressive. The impression we get is very different. Because of his nature of being clear, we don’t get any proof of his romantic feelings, except when he expresses them explicitly. Killua is often shocked when he puts his faith in his words as if that he doesn’t believe the words are being said however it’s not as if Gon is planning to lie on crucial occasions.