User blog comment:BRTE500/I'm out for a Geist/@comment-5426254-20161027040123/@comment-5426254-20161027054147

It's definitely Robin. Mostly because not only of his presence, but Artoria, Hayate, and Akiba were also taking part in this and 3:10 to Atlas, so it rendered his choice moot.

Besides, Robin knows these people from the train RP, and the fact that he's taken time off in Walking with Grimm indicates that he has the capacity to do it again a second time. Call it important for educational research.