Thanks for the chapter :D
I re-read this chapter several times, and realized that Kirishima actually wanted to help the pair from the start, but was masterminding the entire conversation to protect Hikoichi and Nayu's relationship. Kirishima is a master of going along with a conversation to extract information... Let me explain.
His refusal at the start was because, as he said, Himari's face "really isn't the face of someone who's just genuinely concerned about their friend." What he does then, however, is express his empathy: "Well, I suppose I'm one to talk." This is a critical hit against Himari because he knows Himari will start gushing about the two of her own accord, through which he can better understand her actual motives.
Himari then explains that she feels a sense of duty to help the two out of guilt. Again, Kirishima goes along with it until he declines once more. To him, this guilt is a selfish reason to want to interefere, and this interference can only ruin the relationship.
Then, Kirishima uses Himari's pridefulness against her. Notice how he switches up his tone completely and stops going along with Himari. He starts arguing with her about something else entirely, then gets up to leave to make Himari completely desperate. I know this is his intention because he has never gotten off at Akaishi Station. In fact, this is the first time Akaishi Station has been mentioned in this manga.
He gives Himari one last chance, because Himari cares enough about this relationship to get into his personal space and start begging: "Alright, I hear you!" Brilliant move; now, Himari starts talking. This time, her melon bread speech works.
Page 14 is what he has been waiting for the entire conversation. Himari finally acknowledges that the reason why they should interfere is because Hikoichi and Nayu are both the self-sacrificial type, which he also believes. Now, he trusts that Himari will put the interests of Nayu and Hikoichi before her own when interfering, and sees no need to protect Hikoichi's love life from Himari anymore.
Now that he has vetted Himari, this dude really turns away so Himari can't see him smiling to himself... Himari was dancing in the palm of his hand the entire time. Even Uni Student couldn't catch on to his schemes. Truly masterful, Kirishima.
