There seems to be a choice ahead for our duo, go to the after party, or go home. If they go home Kazuya and Chizuru could have a nice heart-to-heart chat on the way, maybe even a confession from Chizuru. That being said, a lot of people seem to rightly think that there'll be a confrontation with Ruka once they get home.
@arimareiji I wonder if Umi tagged Kazuya in his tweet, if so his cover is blown as Ruka follows him on twitter, and will no doubt check her social media after work. While Ruka may have been able to overlook Kazuya not returning her call/texts if he called out sick, her seeing Kazuya at a party in a recently taken photo will definitely garner her ire. It'll be a lot worse if Kazuya's work finds out about the incident, man is as good as fired. Regardless, if Kazuya and Chizuru go home together and encounter Ruka, Chizuru may fed up enough that she'll tell Ruka off. It'd be a harsh move if Ruka waits to confront him about the event at work.
If they go to the after party, they'll inevitably have a run in with Umi and his close friends. Umi could make a move, maybe he asks Chizuru out knowing that he'll be rejected to give Kazuya's confidence a boost. Umi could also just as easily give Chizuru a kiss on the cheek (weird) from the wrong angle Kazuya could misinterpret the event and run home, else Umi flat out forces a kiss on Chizuru, once again leaving Kazuya to return home after misinterpreting the events.
It's hard to get a solid read on Umi, he's basically a blank slate with almost as many red flags as green ones. That being said, this series will probably be remembered for the potential drama in the series, rather than the actual drama in the series, which is probably why so many people projected Umi to be a bad guy, or wish for NTR. But, to play devils advocate for
@ammatrax and
@Revenant62 , Umi did change the phrasing of Chizuru's response from "I don't not like him" to "I don't not like you", adding unnecessary doubt to the phrase, and may be aimed at confusing Kazuya and Chizuru.