@Thelonewolf I guess that the author, if he don't want to be repetitive he can explore the risks of the "friendzone" so he can move this from "fake girlfriend" to "let's be good friends".
He has a good excuse. They are both exhausted after the effort for the film, almost broken so they need money and after all that has happened (and the rest of the plot... helping him to release some burden at the beach as I expected...) she could ask him to don't rent her again... just ask her to hang out... as friends, so they could change their "usual date" into a "Wednesday's friend".
So... the store can explore a new scenario, where they both declare to be friends.
Ruka ends the truce and high the bar pushing him to have sex (again)... but after fail a couple of times, she push Chizuru instead, to make her move... If she wants to be with him, she will accept, but if she wants to be only his friend then Chizuru must help her to become his real girlfriend.
"We both want Kazuya to be happy after all, isn't it?"
Chizuru barely accept, so they start to hang out the three. Ruka overacting with him in front of Chizuru just for "claiming her territory". Kazuya crying all the time because Ruka is destroying his opportunities with Chizuru while at the same time he is a little upset because Chizuru seems to be fine with this, while at the same time Chizuru is more and more upset and broken inside because she starts to admit her feelings to him but just on the inside. She is a good actress after all.
Mami see them again. She introduce herself again but she is shocked when ANOTHER girl claim that she is his girlfriend and his former "rent girlfriend just a friend". After she research a little, she finds that Ruka is (was... but she doesn't notice) another rent girlfriend, so she search for them and confront the group with something like "Don't be stupid Kazuya... They only wants your money. You deserves a real girlfriend".
But... of course, Ruka is not Chizuru, so she explodes and confronts Mami and after some some strongs words, they "fight" just to be separated by both, Chizuru and Kazuya.
While this, Mini is warning both, Chizuru and Kazuya all the time that they are a couple of jerks because it's very obvious that the are in love to each other and this play about "being only friends" is gonna end bad and they are only hurting themselves.
As Chizuru goes down a little more everyday, Sumi sees her, she understand and ask her to be "the fourth wheel" in the group to making things softer for Chizuru with their "friendly hang outs".
Ruka happily accepts because she interprets this like Chizuru accepts once and for all that she is only a friend for Kazuya.
"The more, the merrier". When Mini hear this she self-invited too because he wants to know the new adventures of her "Master".
By chance, they all coincide with all their friends like in the birthday party. They have a inter-group couple after all.
Mami is there... and Kuri too. Mami is angry about Ruka and Chizuru because they "use Kazuya".
Kuri is angry with Kazuya because he never confessed him that his former girlfriend is now his real girlfriend.
After some "sharpen words" everything explodes. Mami tells everybody that they are both "rent girlfriends" and reveal her real name to her friends so all the friends now knows that Mizuhara and Chizuru Ichinose are the same person.
Chizuru flee, and Kazuma try to go for her, but Ruka catch him.
After some minutes of confusing yelling each other, Sumi drops the bomb. She talks like a pro making everybody to shut up, and she is the voice of the reason here.
"If you love someone, your first priority should be that he must be happy. So there is no point in try to conquer the heart of a person that is in a couple that love each other, because in the end, the only thing that you will get it to make him suffer more. And you don't want this if you really love him"
"Don't speak about things you don't know!" - Ruka
"I KNOW. I KNOW FOR SURE... BECAUSE I LOVE KAZUYA TOO"
Something like that.
Kazuya explodes too, and tells both that he is tired of this. He only loves Chizuru.
"Maybe I'm a dumb guy that loves someone that only see me as a friend, but this is what I feel and nothing is gonna change that".
"I love Chizuru. I love her with all my heart! I always loved Chizuru and I always will do!"
"As long as you (Ruka and Mami) are unable to be around me without hurting her, I don't want to know anything about you!"
For Sumi... He only says "Sorry ... and ... thanks for all". She only confirms waving her head while she is crying.
Kuri says "Sorry too... friend. I... cover you here." (referring to Sumi) "Go for her."
And after Kazuya leaves trying to find Chizuru, Ruka and Mami leaves embarrassed, and Kuri comforts Sumi and praised her to be so brave and mature. Mini talks to the rest of the friends that are everybody shocked yet and they don't understand nothing.
So Mini tells "Well. I guess I'm the only one here that knows everything so... Do you want to know what's happen here?", and reveals everything to everybody.
Chizuru disappear. Kazuya goes down again and blames himself again. "I waited too much to confess my feelings. NO! I never have a chance. She is only a friend and I failed to her... blablablabla"
Mini, Sumi and Kuri (that become a support for Sumi... and she greatly appreciates) try to find her for themselves.
Sumi knows how to find her. They found her in her aunt's old house. After all, is her house by heritage now, and Sumi hopes she will visit her aunt's altar to pray her.
Her friends confronts her.
"You love him!" says Sumi with determination
Kuri - "Don't be stupid!. Did you know how difficult is to find a real love? Why do you think that we rent girlfriends? When you can't have a real love, even a fantasy can warm you heart. But you can have the real deal! The only thing that you need to do is to accept it!"
"Yes... I love him. And I know he loves me... But in the end... It doesn't matter because he only loves me... like a sister" ( a thing that he said in the "friend time")
Obviously the three friends sighs.
"You both are a pair of idiots". - Mini
"Yeah... you are definitely made for each other" - Kuri
Mini shows a video. Of course, she recorded the whole confession of Kazuya with their friends.
"I love Chizuru. I love her with all my heart!..."
She returned... confess... and all ends happy.
In the aftermath, we show how to Sumi ask Kuri to help her to train to be a good "rent girlfriend".
"Sure... What's your price?" - Kuri
"You are helping me. It will be free for you." - Sumi (writing)
"But... If it's free... It would be like... I would be... like... a ... real... boyfriend..."- Kuri
"I guess?" - Sumi writing while blussing... and smiles
In other scene...
Kazuya is with Chizuru disguised as Chizuru Ichinose (glasses and braids) and talking to some of their friends about their previous meeting and confession with his grandmother.
Ruka is stalking Kazuya from the distance hiding under a bush. After all, she doesn't lay down. But Kibe appears from behind.
"YOU AGAIN? It's the fifth time I catch you chivvying my friends! STOP ALREADY!"
"I'm not chivvying! I'm.... waiting! Sooner or later she will drop him... and when that happens I will be there for him!"
"Find another one! My friends are happy together. Stop... NOW!" says and he walks away angry.
She sticking out her tongue to him and later, she checks her phone. Her beat rate is fast.
"Again... It's real. " - she babble and smiles happy.
And a last scene. Mami is in bad mud on the school.
- "And here we have the last member of the former harem. She seems to be the worst for it." - says Mini that appears to be recording her with her phone
- "What's your problem"
- "I'm recording master's story. Just a moment. I almost finished!"
- "Get lost!"
- "You are in bad mud, eh?. Do you want an advice?"
- "No."
- "I will do anyway. You start all of this, but you haven't move since then. Well... maybe that beach kiss... but... Anyway... You messed up. Accept it and move on! Kazuya and Chizuru are happy now. Sumi seems to be fine. Ruka is trying to find a new love... Do yourself a favor and do the same."
Mami don't say anything and Mini start to walk way
- "And next time don't dump a boyfriend if you love him!" - Mini says at the end.
----
There is enough material for 50 chapters more at least. And in the "friend story arc" there is room for some jokes and (filler) mini stories. But... yeah... try to overstretch this too much it will ruin the story at the end. It's better to finish it with a proper ending.
P.D. I'm not English native so... sorry for the mistakes.
