Okay, there's seriously so much Sirius characterisation in here that it took my breath away at times, it hurt so much. Tonks, too, of course, but Sirius holds a special place in my heart, so it's for him I felt the most.
I love how you don't know anymore who actually is the victim and who is the abuser, because Sirius is majorly fucked up, and Tonks... Tonks tries to save who can't be saved.
She is certain that the next time, she will break through the barriers and If she can be patient for a little while longer, she'll have it all. - ouch, ouch, ouch.
The portrayal of their relationship also sheds a new light on the whole Remus/Tonks thing later, because of course Tonks attaches herself to the only other person who was really close to Sirius.
In a nutshell: damn, but this is gorgeously painful!