Ulrich has always been a very private boy, more than a bit shy thanks to the high expectations that surround him from every move he makes to every word that comes out of his mouth. Ulrich does not tell his friends everything, never intends to.
He never intends to tell Odd that part of the reason he stopped him was because he remembered being on the other end of a blade himself (he always did it in places no one would see because his father would have beat him bloody, he was sure, if he'd done it in a visible place, and he couldn't get away with extra clothing like Odd could). He never intends to tell Odd that one of the people he saw fall into the darkness was himself from the other side of the mirror (he had no razors, only sharp corners and the promise of a bruise he'd feel whenever he moved just the right way, the occasional cut from rough housing that he couldn't keep his fingers away from because the pain was good).
He never plans to tell anyone about the scars they actually would be able to find on him. The most obvious is on his hip, an angry mark that likely would have killed him had he attempted it on his wrist. He hadn't though, fear of his father keeping him secretive as he clutched the strange blade in his hand. He'd simply dragged it along his skin, again and again along the same line, and it cut, almost too far but in the end it wasn't so much that he couldn't handle it, managing to stop the bleeding and to wrap it for a while.
People forgot there were many ways to hurt yourself. Scratching yourself raw, disturbing your wounds, giving yourself non-intrusive injuries. These were the methods that Ulrich had preferred, the ones that would sit in his belly for as long as he lived as some of the things he really wished he hadn't done. It hadn't stopped, not really, until he'd settled in at Kadic. Once the pressure from his father was dimmer, the threat less present, the pleasantness of the pain was less, and he found himself almost losing interest in it, though he did relapse at times, found himself pressing at a bruise he'd gotten in football and the like.
He forced himself to stop completely when he discovered Odd's habit though. Odd didn't need to know that he wasn't the only one who used that special drawer. Odd wasn't the only one who needed to know the others were there for him, but Ulrich was used to suffering in silence, and it was easier to help someone else than it was to help yourself. It was easier to make Odd accept his help than to accept help from any of the others. Ulrich knew exactly what he had done, and why he had done it, and that most of the things his father said weren't true (not completely). Knowing it rationally and knowing it emotionally were two very different things. Ulrich didn't tell anyone.
"Ulrich what's this?" Aelita asked one day, pointing at a mark on his shoulder. They were all sitting around, enjoying the day that wasn't quite spring and wasn't quite summer, and Ulrich had taken off his shirt because it was getting quite hot. Ulrich barely stopped the wince in time, but he managed.
"Burn scar," he said simply. The others raised their eyebrows at that.
"How'd you get a burn scar on your shoulder?" Yumi asked curiously.
"Oh, I had to blow dry my hair for some reason or other- can't remember why- and it got too hot. I think it broke. Anyway, it ended up giving me a second degree burn, but it healed up nicely." He lied. None of them seemed overly concerned, and Ulrich knew they wouldn't be. It wasn't unusual for someone to just be clumsy. People forgot about the little things, forgot that you didn't have to be obvious to hate yourself. Forgot that there were ways to make it so no one looked at you like you were glass (they looked at Odd like that sometimes, though they didn't realize it). Everyone always forgot those things, but Ulrich never, ever would.