Dear fellow lovers of Japanese language,
I've come across this dialogue in a visual novel:
The implied meaning is unambiguous here, as it is that they should stop talking secrets and act more like students.
However, I'm at my wit's end with the grammar in the second sentence. Is しとこう a volitional form of しとく (a shortened ～しておく)? That is, does 秘密の話はこのヘンにしとこう。 carry the meaning that they should put these stories down [in preparation] for what happens in the next sentence? It would make sense to me this way but I'm very inexperienced with Japanese language so please correct me if I'm wrong.
Thank you for your patience.