Manga Like Between Two Floors

When Jae-Jeong Sin’s dad rents out part of their house, he loses his favorite room, and gains a grudge. The tenants? A single mom and her daughter, A-Rin Woo. Things spiral when Jae-Jeong discovers their parents are having an affair. And, turns out, A-Rin just learned about their affair too. Bound by this dirty secret, Jae-Jeong and A-Rin grow closer, even as resentment simmers. As secrets pile up and tensions rise at school, the two form a dangerous pact: if their parents won’t stop the affair, they will. (Source: WEBTOON, edited)