Mr. Kim, 
Thank you for taking care of my fox. 
She has a hard time with doctors so I appreciate you caring for her. 
However, I would like my fox back. 
As a human with your own pets, you should understand. 
I will be coming for her soon. 
Red
"I received this letter on my desk after my shift, Minsoo said it showed up at the front when she came in." Jin was now pacing the floor, Namjoon holding me even tighter to his chest as he held me on his lap, the movie long forgotten as you both listened to Jin.
You should have known that Red would eventually begin to target your new family. You didn't realize just how far he would go to get you back, to make you his. But you were never his to begin with. 
"Okay... Hobi should be back any minute. Let's wait until he gets here and have a family meeting. We all need to be a lot more careful. Jin," Namjoon spoke, now turning to look at Jin again. "You can't go back to work. If this letter showed up, and no one saw anything, that means that he could just as easily slip in and harm anyone." Jin nods, your safety, and the safety of the family means more to him than his job.
You only needed to wait a couple more minutes before Hobi, Jungkook, and Taehyung rush in. A letter was also in Hobi's hand, Jungkook and Taehyung looking fearful as they cling on to each other. The ruckus they caused coming in also alerted Jimin and Yoongi, now bringing everyone into Namjoon's room. 
The room fell into silence at the sight of a second letter in Hobi's hand. Yoongi took one look at the letter on the bed and the one being held by Hobi and growled, lunging for you, and bringing you into his own hold, face in your neck as he scents you. His grip was tight against you, as if preventing anyone from taking you from him. 
"Have you opened it?" Namjoon asks, looking directly at Hobi. 
"No. I was checking the mail, and found this letter addressed to me. Red ink on the envelope." He answered, moving his fingers underneath the seal, and ripping it open, reading the words on the paper. His eyes quickly narrowed, jaw tensing up from what he was reading. You could see Jungkook and Taehyung, who were still behind Hobi, reading the letter over his shoulder, their own eyes widening. 
Mr. Jung,
Your investigation is causing somewhat of a hinderance to my plans. 
You have my fox, and despite the way you help care for her, she is mine. 
I am the only one who can keep my fox safe and cared for properly. 
You may claim to be her mate, as well as your pets' mate, but you are lying.
My fox wouldn't stay away from me for that long.
She would be back by my side if it wasn't for you. 
I will be coming for her soon.
Red
Your stomach churned as Namjoon read the letters aloud to the room, your body freezing at the words on the page, claiming you were Red's. A growl was building in Yoongi's throat, the vibrations felt against your back.
"We can't let him get away with this. He knows where we live, and he knows where the boys work." Jungkook spoke up, his training coming back to him as he assessed the situation, eyes on the letters, the flourishes of the handwriting and the wording of the sentences.