Sigh I wish Nagatsuki would just move on already, reading about her pining after Ookuma because of pure infatuation is honestly so frustrating. I hope she's finally realized her chances after Ookuma admitted that he didn't see any of their get-togethers as 'dates'.
I want to give Ookuma the benefit of the doubt but he's super sketchy. Like FredFriendly said, he has had many chances to clear the air between them but instead he isn't. There's nothing wrong with at least admitting that they knew each other in middle school. I can't decipher what his motives are but I think the purpose of his character is to address and resolve what happened with Chiyo in the past.