@Mivas You need to understand Asian culture. Men and women that are only friends don't go to each other's house alone. It is really inappropriate. A girl can go to a boy's house only if she is with a group of friends or vice versa. That is why romcom always make such a big deal when a character goes to another character's room. A man and a woman stay at each other's house alone like Narumi and Hirotaka means that they are dating and already took it to the next level. Narumi and Hirotaka's relationship already advanced a lot and other details are implicated in a way that if you are an Asian or familiar with Asian culture, you can understand without the manga showing them.