Do we know if Tsukishima's the only one of Lieutenant Tsurumi's men who speaks Russian?
If he is, then this couldn't have been a 7th Division plot, because at least 2 people were speaking Russian in the last 2 chapters.
I do feel like the kidnapping could've been the 7th's doing, though.
There's still the possibility that Tsurumi's men went undercover to infiltrate the real kidnappers, though.