i think gon first, but killua more visibly and… viscerally.

killua is, from the beginning, a lot like—“hey, this is a kid my age! who can keep up with me? that’s dope!” it’s not a matter of love or crushes, because killua has no experience with that. he’s never even had a real friend! so i interpret a lot of his initial interactions with gon as curious, interested, amused, etc.

that’s why killua is so focused on saying, i want to be gon’s friend. perhaps at that point his feelings were starting to become more serious (what we would consider love), but his fixation is platonic. he wants to have a real connection with someone that interests him, that’s like him, that can connect with him.

i see gon’s FURIOUS reaction to that—his insistence on their friendship, him storming all the way to the zoldyck mountain, his willingness to be berated, beaten, and tested—as love. absolutely love. and i think gon is only partly in tune with that, but yeah, i definitely believe gon fell first.

but when killua gets to that same point? holy shit. it’s heartbreaking, it’s innocent, it’s gentle, it’s devoted. not to be cliche, but it really is that killua fell slowly, then all at once; he was on the brink of it for a long time, but eventually it’s all he can think of and dream of and see: gon. his LOVE for gon.