This is seriously just chapters 49 and 50 again. The English title of chapter 49 was "The Girlfriend and the Confession," which is probably why this is labeled as Part 3 instead of Part 2. In chapter 50, she goes into her apartment and sits down and says "stupid" with a concerned look. In chapter 174, she goes into her apartment and lies down and says "I'm so stupid" with a concerned look.
I know romance manga goes slowly, but this is more than 120 chapters with no appreciable progress between the main characters. They're no closer than they were in August 2018.