Kei-chan no Koibito wa Futari Iru

It's been two years since Saki Miyamoto moved to Tokyo. She is so occupied with work that she doesn't even know how to make friends, let alone find a boyfriend. Then, she runs into her childhood friend Ke-chan for the first time in more than 10 years, and is invited to join him in a shared house in a high-rise apartment. Saki decides to join, hoping to meet some new people. However, the other residents there besides Ke-chan are both Ke-chan's lovers...? Saki and company living together in a titillating story about a new form of love under one roof!

(Source: Comic Days, translated)