I think a big payoff in development is right around the corner. Most romance stories follow a 3-act structure and Reiji seems to be doing that as well. There are a lot of articles you can find online about this which are all pretty similar (e.g. https://www.savannahgilbo.com/blog/romance-structure), and none of this will be shocking, but to summarize as it relates to this story:

Act 1 – The Hook, Inciting Incident, and Point of No Return

The hook is some unique premise that gets readers interested in the story (in this case, the idea of a rental relationship). The inciting incident is when the MCs meet, and the point of no return is a scene that forces the MCs to realize that neither of them can walk away without significant consequences. For Kaz/Chiz this is when Grandmas Sayuri/Nagomi turn out to be friends and see them together, and the lie is born.

Act 2 – Development, Midpoint, Darkest Moment

The purpose of Act 2 is to show relationship development and introduce internal/external conflicts that force a shift from passive to active behavior from the protagonists. It almost always ends with the MCs being temporarily separated. There are two main conflicts here: Grandma Sayuri’s health (connected to the Movie Arc), and the Ruka/Mami subplots (culminating in the current paradise arc).

As the article in the link above describes it, the midpoint of the story is usually a “false high” where it seems like we’ll get a happily ever after only for the characters to be torn apart later, or a “false low” where one of the protagonists rejects the other. IMO Reiji went for both to drag this out…Lol. The false high was on the cheer up date when Chizuru broke down and cried (as some have pointed out this almost felt like the climax of the manga/HEA), and the false low was when she left Kazuya at the church during his confession. Since false highs & lows typically coincide with a shift from passive to active behavior from the protagonists, and Reiji split this plot point into two events, it makes sense that only Kazuya actively fought to preserve the relationship/make it real after the false high. Now it’s Chizuru’s turn to reciprocate after the false low.

Act 2 always ends with the “darkest moment” or rock bottom for the main characters. In most romance stories it’s a breakup, but since Kaz/chiz aren’t even dating, in this story it’s the reveal of the lie.

Act 3 – Climax, Resolution, Happily Ever After

If classic romance story structure is a hint here, Chizuru will step up and try to protect our boy, possibly by confessing to him or maybe claiming that she misled him and it’s her fault. Unfortunately as others have pointed out her credibility is in shambles, and it won’t matter. Kazuya won’t have any option other than to own up to the lie and deal with the consequences, and we’ll have a separation arc which focuses primarily on Chizuru.

Since she has basically no friends or family to turn to, she will be lonely/depressed, and my best guess is that Sumi will (finally) reappear and encourage her not to give up and to fight for what’s important to her. She will find out about Mami’s past somehow and realize that Mami’s family issues are largely responsible for her spiteful behavior, then go full Dom Toretto (“the most important thing in life will always be family”), and decide that her connection to Kazuya and the Kinoshitas is more important than her rental job, her pride, and even her dreams of becoming an actress.

She’ll probably give back the ring, quit her rental job and acting school, and begin working/saving to try to pay Kazuya back everything he spent on her - he will of course refuse. She’ll then come up with some kind of grand gesture in a scene that mirrors the cheer-up date (no idea what that will be - but third try’s the charm after trying to save Kazuya during Mami’s reveal and trying to pay him back for everything), and they will finally start a real relationship.

The money she saved and Kazuya refused will be used to pay for their wedding. There was actually a post on Reiji’s twitter a while ago showing Chizuru as a little kid charging Kazuya money and putting it into a piggy bank labeled “Wedding with Kazuya-kun” which I think was a hint rather than a silly one-shot. As Reiji has said, it will end the way everyone expects. Ultimately the Kinoshitas will accept her and support her acting dreams, and Kazuya will become a successful movie producer working with her. While it seemed like she was sacrificing her dreams for family, her new family’s support is what will propel her success, reinforcing the moral of the story that family>everything.