Gon knew there was no going back to the way things were. You can't exactly apologize to someone for destroying them and then expect them to act like nothing happened, no matter how much he would have wished it to be possible.
He wanted to say it wasn't him, that he wasn't in his senses when he said what he said and acted like he acted, but it was.
It was him.
It was him yet at the same time the farthest from himself as possible.
He only feared he would never be able to explain that, and for evidently valid reasons.
...
He didn't introduce him to Ging.
Killua almost wanted to punch himself for remembering such a random conversation.
"I will introduce him to Killua, my best friend in the world!"
By the time it would have been possible, he wasn't sure he was anymore.
By the time it would have been possible, he wasn't sure if Gon was even back, or who Gon was.
He wasn't sure he'd ever known him, and it scared him.
He didn't hate him, not at all.
He didn't resent him per se either.
He just didn't think he could handle things as they were.
He had to leave.
If he didn't leave, this whole situation wouldn't have the space to breathe and it would slowly rot, only to die in the end without a single sign that it was ever something beautiful.
Besides, he had Alluka to think about. Killua had found his own purpose: he had a sister to protect.
...
Alluka asked him several times why he hadn't met up with Gon yet. The first time it was six months after they'd gone their separate ways; the second time was but a few months after that.
She didn't understand why her brother still hadn't gone back, but she figured perhaps it wasn't yet the right time.
The third time it was after a year.
She figured he was scared.
Then it was after two.
He pretended not to hear.
Had it been five? Six years?
He eventually stopped responding, and she eventually stopped asking.
Killua did talk about him though, Alluka remembered. Killua talked about Gon like a distant memory, like the ghost of adventures from a faraway dream. There was no bitterness in his voice when he mentioned him, only... Gratefulness. As if he owed Gon's ghost for who he was in the present.
Alluka didn't want to tell him that if he kept waiting for a right time, Gon might actually become one.
...
Hisoka was the one that told him.
Killua didn't believe him.