You know how a certain type of the best painful, angsty dramas of hurt and healing, that have occasional terribly heartwarming moments and a softhearted conclusion?
This story pulls off the neat hat-trick of having those warm moments of respite and healing without actually going through all the terrible angst first. It's really quite something. I've seen people try to do this a lot in stories, but almost none that carry it out so successfully, to drop you right in the midst of things while things are getting better for the characters and have it feel just like that instead of just feeling like, "by the way, there's some dark past stuff or other you should know about".
The story's not perfect, but it doesn't matter.
....The unrelated (and maybe deserving a yaoi-tag) one-shot that is ch. 6 seems like an absurdly ham-handed generic BL story by comparison. It would be better if it weren't included in the volume, it's like having the last course of a well-thought-out meal being followed by a microwave dinner.