That's exactly how it is, and it's intentionally designed like that... That's why this game is called, because every character is connected to someone... If each character had an individual route, then the story would be less exciting... Because it's not a harem game , so if you like more than one character, you have to decide who to choose...Since you like Iris, you can unfortunately only reach her in two routes, but even then another girl is in the foreground (Alex's route and Layla in Alex's secret route). Erynn has her own route, but then there will be little game content... You have to make the decision...