Nekomimi Shounen Maid no Ai suru Himegoto

Levi, a young boy working as a maid in a mansion, loves his master, but always acts cold in front of others. One day, he protects his master when he is about to be attacked at a party, and elegantly repels the bad guys. As a reward, Levi becomes a lovey-dovey cat only when he is with his master, and you can see his lewd behavior.