Wen Qinxi hadn't been looking where he was going running away from his mother after taking all of her twinkies from her handbag. At that time his mother had developed an unhealthy habit of eating twinkies at any given chance which is why they took turns robbing her.
They had had enough of her constantly asking them if she had gained weight and when they answered honestly she would call them unfilial. If they lie she would say she didn't raise liars. So stealing her stash was the only way to go.
He could still hear her yelling as he dashed into a corner. His hasty actions meant he collided with Qie Ranzhe falling straight into his arms but because his mother was coming into the school grounds he apologized and gave the contraband to Qie Ranzhe before vanishing in an instant.