Nico was your best friend, but sometimes you just needed to be alone, which he completely understood. What he didn't understand is why you seemed to be acting like him when he had lost Bianca. It was like you were blaming yourself for something and distancing yourself from everyone for, seemingly, no reason.

What Nico didn't know was that you had just lost your sister, and you believed that it was your fault. You couldn't save her from a hellhound, but she had chosen to sacrifice herself to save you. That made you feel even worse about the whole situation.

So, instead of talking about it like most people should, you bottled everything up and hid your emotions. It was like you were running from yourself. From your own past.

Nico decided that he needed to get to the bottom of this, so he confronted you one day, even though you clearly didn't want to talk.

"I know you don't want to talk, but I'm not going to let you wither alone. You will tell me what's wrong even if you don't want to." Nico said coldly, but with a hint of understanding and sympathy that calmed your racing heartbeat.