@Istvan90623 Because nao misunderstood him. Since this is eiji’s pov, you can see how his thoughts were different. In nao’s pov on the first few chapters, he thought eiji sincerely liked those older girls but saw how he never confessed and thought that was pitiful. In reality, eiji just didn’t truly like those girls/wanted to date them.
So while it technically true that eiji didn’t truly confess his feelings back then and nao was aware of that, nao that it was a completely different context (different girls), so he sincerely didn’t know about izumi or how he felt about them dating. If anything, he thought izumi liked eiji, but eiji had never shown that he liked izumi (tho he did wonder when he met izumi, but he denied it)