Based on my understanding, Alex is hinting to Nori that he likes Chris onesidedly. Chris said that he shares about his lovelife to Alex. I supposed because of that, Alex concluded that Chris is straight, because he only dated girls in the past. Therefore Alex thinks his feelings will never be reciprocated.










The story is same with this one
https://www.mangago.zone/read-manga/kanjou_spectrum_yoneda_kou/