The husband is again exposed to his company as a cheater, this time his boss doesn't forgive him and gives him 2 options, resign or relocate to the countryside branch. He relocates but Karin doesn't follow him there, they breakup. Sumire then exposed his affairs to the locals and he becomes enemy #1 to everyone there. Sumire ghosted him and he was so desperate that his health declined so much he had to be hospitalized.
Karin on the other hand now alone with no money accepted Sumire's advice to become a rental girlfriend. She enjoyed the money and attention of wealthy guys, not knowing absolutely everything was a setup for her to become a prostitute. Which she does end up becoming, sleeping with even ugly bastards...
Anyway, during Karin's desperation Sumire reveals to her who she really is, and tells her the whole country will know their story at midnight when her book goes on sale (this was a great scene). She wrote everything in detailed about them, it even has a bunch of pictures, and she made it very cheap so everyone can buy it. So it became a hit over night, and when the husband read it, he lost his mind and ended up in a mental institute...
Karin didn't know what to do, even her sugar daddies dropped her after her skin and hair became ugly from the stress. Then she hired a Yakuza type of guy who does human trafficking. They kidnapped Sumire and while holding her hostage Karin had a breakdown. She tried to kill her with a knife but the Yakuza guy tried to stop her, since Sumire is valuable to him, but Karin ended up accidentally killing him. While panicking what to do, she lunges at Sumire to kill her to but Kiritani pops up and takes the stab in the stomach. He tells Sumire he hid a GPS device in a charm he gave her. The police arrive and Karin is arrested for murder.
Kiritani survives, and after a small time skip he and Sumire are a couple and work at the bar together.
There is also an interesting sub plot with a rich ceo playboy, but i'll leave that part for you to see in the manga...