I'm SO glad Koito survived. I really liked how Tsukishima betrayed what was most important to the mission to save him, I think it shows that he does really care about him. However, I think it's pretty clear that Koito is eventually going to betray Tsurumi, (A+ development by the way, I love how he's growing as a person) and when he does, I feel that Tsukishima is going to be somewhat of a wildcard when it comes to which side he's going to fall on in the end.
As we have already seen, Tsukishima is a husk of a man operating on the belief that since he had to let go what was spurring him on to live (hope that the curly-haired girl was still alive), his only purpose in life is now serving Tsurumi. In the chapter where Inkarmat gives birth and he and Koito get into a confrontation, he says that it's "too late" for him to turn back since he's already killed so many people on Tsurumi's orders.
The only reason Koito was able to talk him down in the scene above was because Koito reassured him that he was still going to obey and serve Trsurumi. But, if I'm correct in my prediction of Koito's eventual betrayal of Tsurumi, then I think soon we're going to see Tsukushima have to choose between his loyalty to Tsurumi and his affection for Koito. And I can't wait.