It sounds like you’re referencing a specific adult manga, doujinshi, or hentai work from around 2021, possibly by a circle or artist named (裏通り) or with a title containing “nukemichi,” “ane bitch,” and “harem.”
The narrative centers on his interactions with the older female tenants in the building, primarily:
Several independent V-Tubers in late 2021 adopted the "Ane from the Backstreet" persona. Their streams were low-energy, late-night chats where they'd give life advice, cook simple meals, or play retro games. The "harem" aspect was meta—the viewers were the harem, each receiving virtual ane affection.