This is now the third time this old story has been hashed over, the first time from Chiyo's perspective in chapter 14, and again in chapter 52 from Ookuma's perspective. We're now 170 chapters in and this headache just won't go away. Where are those nay-sayers who, back in the comments section of chapter 156, said that Ookuma and Chiyo's "past relationship doesn't matter" and that the "Ookuma thing was never really relevant and it's just in the past." Oh, if that were only the case then there would be no reason for Chiyo to hide it from Igarashi, would there?
Well, let's hope that Nagatsuki can at least put 2 and 2 together and realize that she's got no hope with Ookuma and that he's just been using her all along as a way to get closer to Chiyo.