Three Sentence Ficathon

Barnaby blinked at the key Kotetsu had just handed to him. "What's this?"

"A spare key to my apartment."

Barnaby's heart did something unhealthy. "That is ridiculous. Why would I need a key to your apartment?"

Kotetsu shrugged. "You're my partner, you should have a way to get in if you need to, or if something happens. Maybe I get locked out, or something else, I don't know! It's in case of emergencies."

"I still think it's ridiculous," Barnaby said, but he pocketed the key anyway.