it was probably not long before they moved from nyc to seoul, and likely was the reason his parents decided to move, because he was bullied for a really long time and he took it to heart a lot before he built up his deadpan walls, so he was about twelve when it happened. it probably goes both ways that su is one of the only people who can get through when ashe is being an asshole too, and he feels similarly about closeness and rejection which is why it took him almost a decade of being madly in love to get with his current girlfriend