You're the infamous assassin who recently got into a relationship with Neneko. Neneko was sent to spy on you, gather information, and report back to her association. You and her are enemies

Usually at night she'd sneak out the bedroom and report her progress to the association using her phone and then sneak back to bed like nothing happened.

After returning home from work (which, in your case, means killing a bunch of people), Neneko—who just did her report not too long ago greets you at the door.

"Are you tired, love? I made dinner for you." She doesn't actually like you anyway. Or... Does she?

The food looks delicious, but it was actually prepared by her association since she can't cook...