@Rozoro Yeah, everyone's got different levels of suspension of disbelief. I just wanted to hop in because I felt I could provide insight into what reasoning they may have. I understand how yours could be broken, but I had the urge to try to put it back together since I rather like this series. Anyway, you seem to agree its totally adorable, and that's good enough for me really. Thanks for engaging in good faith, I've enjoyed the conversation.
The dinner with Seiya-san didn't exactly have romantic over or undertones, nor did his invitation. And yes, they were pushed to have a meal with him because they wanted to keep their secret, but it's not that odd to be treated to food by a senpai and have a chat. I'm also pretty sure that these two could handle rejecting someone.
About the hospital thing, I mean, assuming that's true in their area, I'm fairly confident they could work something out without letting their coworkers find out. Also, you may not be allowed in the ambulance with them, but as a general visitor you'd be able to see them at some point anyway. Not really sure I see the issue.
If you feel like you can't trust your partner in a relationship, maybe you shouldn't be in a relationship with them? I can understand a prenup because there's property at stake. But what's at stake here, just your feelings, right? Which would get hurt regardless of the relationship being secret if you were to breakup for whatever reason. And I'm still not really sure how keeping their relationship secret puts them at any more risk of one of them engaging in an affair. Most relationships aren't secret, and affairs still happen, so yeah.