On the darker and graver look of things, Northern had just grown paranoid about people, especially when it came to believing them.
His immature fear of being used, outsmarted, was making him cynical.
Or was he cynical to begin with? Then became immature and paranoid to top it.
There was nothing entirely wrong with being cynical, but his preconceived mindset that every human was a liar of some sort, and would only use him for their own selfish agenda without consideration for him or his wellbeing... well, needed a fix here and there.
In the end, Northern agreed to the deal and returned to the estate where other students were staying.
He ended up pawning the items he wanted to. Nothing much actually; he just gave away the old items that had been quite useless to him since Hao had taken the useful ones in exchange for some really, really useful items.
Take the necklace that wouldn't come off his neck for example.