(Thanks to the joys (not) of having his memory snipped, he doesn't have a clue that Akechi's life is on the line back in their reality. He had been so adamant about being alive all this time, just unavailable, that Ren hasn't thought for a second Akechi's what Maruki "did for him".

... Mostly because he wasn't quite interested in hearing what Maruki thought should be his ideal reality. He can make one for himself.

The words catch Ren off-guard and he found a lock of hair to curl.)

I know you want to leave. I'm not keeping you here like you're a hostage because I want a resolve out of that. Wouldn't be fair to you.

(... ! He speaks!)