"Wha-? What? No! I mea- N-no- we, we're n-not-" Haneul bursts out laughing at the confused reaction, right now really wanting to see Sangcheol's face. He thought the joke is obvious, but it seems, it is too advanced for the other. Should he explain it? Sangcheol is so confused right now. Though, on second thought, he should leave the alpha like this.
As a revenge. For making him have his anxiety attack in the middle of a boring island.
"Your mom hates you?" After the long silence post-laughter, having his portion of fun, Haneul decides to change the subject. Even though he made up his mind not to care, what Sangcheol just said really piques his interest - the fact that his mother acted the way she did because of his friend, instead of him as he initially thought. Although it could only be Sangcheol's way of making him feel better, there is no harm in asking.
"No… she's just, she thought we're seeing each other."