It makes sense. It would have been stupid to consider any other reaction to what he had said, but the words still cut into Donghoon, hard. Of course Mujin didn't want to revel in the good times, they would be forever stained by his true identity now, forever cloudy with the smog of betrayal.
And the rose coloured glasses Donghoon had worn to look back, to forget which moments had been him, and which had been Joonsu, which moments had been reported, and which kept secret... those glasses were gone. Everything was over.
He flinches when the gun clatters onto the coffee table, but doesn't look at it; he can barely stand to look at Mujin, let alone a symbol of his lies. Honour. He had thought himself the honourable one once, still did, occasionally, and when Cha Giho reminded him how many people he could help, when he had struggled to justify the crimes he committed, before he'd fallen in love. After that he had just been concerned with doing what Mujin wanted. Could he call himself a cop, now? Could he call himself a gangster?
What name would they carve onto his urn?
"I wanted to tell you, so many times." Because it was true, he had, he'd almost let it slip a hundred times, over the years, lips parted, then closed when this reaction would come to mind. "Mujin I was terrified. Of losing Jiwoo, of losing... of losing you. You have to - no... sorry, I-" He had never had to argue with this man before, and he was failing spectacularly at it. "If I had stopped reporting, they would have pulled me out, and arrested you. If I had... told them I loved you, they would have pulled me out, and arrested you. If I had told you..." His eyes finally flick to the gun, "You'd have shot me in an instant, and I'd never get to say sorry."