I get the feeling that this won't just be a one-off occurrence and it might just turn into an inverted version of one of my least favorite tropes where one of the main characters (usually the female lead) spends more time with a "friend" of the opposite sex than with the s.o. doing things, like in this chapter, that they should reserve for doing with their lover. I am guessing that Nanako would not have been happy if she knew her boyfriend was spending so much time with another girl doing things he should be doing with her.
People misunderstanding Iori's character is just frustrating. Iori was introduced to help progress the plot even more and develop Eiji's character rather than being a 4th rival. people like @fredfriendly here are just dumb close minded fckers. Closure is important rather than regret, if a couple breaks off because of this kind of thing then their relationship is just too weak and fragile so they dont trust each other. A nice closure nonetheless.