Inu x Boku SS

Synopsis

Since his family name was known to be born from an evil bloodline, Soushi was secluded inside a shrine as a child. A year later at a party, a woman allows him to work for her in her house, where he is to serve a young Kagerou for a living. It is revealed that Kagerou told Soushi to respond to the letters sent from his fiancée, to which Soushi believed her to be very perceptive. When Kagerou showed Soushi who his fiancée was, that being Ririchiyo, Soushi was surprised to see a spoiled rich girl write letters so keenly. During the summer, they continued writing letters to each other, and Soushi realized his feelings for Ririchiyo, but he started to feel guilty for faking Kagerou's personality. After hearing that Ririchiyo moved inside the Maison de Ayakashi, that is when he decided to become a Secret Service agent. Ririchiyo already knows that Kagerou was not the one who responded to her letters, but she is shocked to find out that Soushi was actually the one who did, which confirmed how Soushi knew so much about her in the first place.

(Source: Wikipedia)