Love and War

Post-war.
Twenty-one-year-old Harry Potter is disillusioned with the Auror Corps as he has some residual spell damage and can no longer partake in active field duty. The young wizard is regulated to his desk at the ministry, and thinks that he should be doing more and not getting "special treatment", as it were.
Severus Snape, now the Deputy Headmaster, has become a bit of a recluse, and is only seen in his potions classes or at mealtimes, and spends the rest of his time brewing. None of the professors can get through to him, as the man doesn't seem to want to listen.
Minerva McGonagall, now the Headmistress of Hogwarts, decides that enough is enough, and so she hires Harry as the new Defense Against the Dark Arts professor, in the hopes of filling the position, and getting Severus out of his funk.