"Based on who lives here, I'm guessing more murder." Ren is including himself and his near-inevitable tape when he says that, which is why he doesn't sound as indifferent as he might otherwise. He sticks the new tape in the VCR and returns to Goro's side as it starts playing.

It's immediately obvious who the memory belongs to, which is convenient. They haven't yet had to play a guessing game. That's the only good thing Ren can say, however. He doesn't particularly care about invading Falcon's privacy, but watching this happen... Falcon trying to fight, only to be brought up short with a word from Shido, unable to do anything but comply despite his horror.

Ren watches with a fixed expression. I own you, says the Shido on the tape, and he flinches; his breath stutters when Wakaba Isshiki appears. Her death is different from the death of his world's Isshiki, just like what happened to Falcon isn't the same as what happened to Ren. But Ren can see the threads connecting them. Alternate worlds, but echoes of the same events, over and over, and always Shido at the center of it.

He doesn't quite realize how rigid his posture is. I own you. He's heard that before, from the same lips.