I love this! It's such a very emotionally true story, and quite frankly, for this period in Snape's life, Kingsley is really one of the very few people who makes sense for Severus to be partnered with - and not only because he's somebody who's in a position to know (and keep) secrets.
Meanwhile, I *really* like stories in which *both* Snape and his partner or partner-to-be) are competent wizards and clever men - and this fits the bill perfectly; I loved seeing Kingsley get the drop on Snape in his own quarters (for his own good *g*), even though I'm going to be generous to Severus and assume that never would have happened if he hadn't just been hit with the Cruciatus.