Want to live in the East Village? Get a roommate! Yes, even if you’re a retail store. At 309 East Ninth Street, Musu’s handmade soaps, candles and hats now line one side of the narrow space and Marjory Warren’s clothing and jewelry graces the other.

Why did the former neighbors move in with each other? Allow us to explain.

When Musu’s lease at 305 East Ninth Street was up last year, owner Maima Sonii was forced to seek a new home for her girly gift shop. She found it just a couple doors over, in the space that — funnily enough — used to house her defunct clothing shop, Miss Sonii.

Marjory Warren, the boutique that replaced Miss Sonii at 309 East Ninth Street about a year and a half ago, happened to have some room to spare, and sharing it with the space’s former tenant seemed like a good idea. “Economically, it’s been slow, and then Sandy hit,” said Christine Warren, co-owner of Marjory Warren. “I don’t want to speak for everyone else but it was like someone pulling a rug from underneath your feet.”

Earlier this month, after a false wall came down, Ms. Sonii finished moving Musu into the elongated store, where she now gets half of its space and pays half of its rent. The store’s front sign hasn’t yet changed, but the arrangement already seems to be working.

Daniel Maurer Musu at right, Marjory Warren at left.

“We’re very distinct styles but I’m seeing a large crossover in clientele and they’re both appreciating both [sides of the store],” said Ms. Warren, noting that her brand’s middle-aged devotees tend to be older than Musu’s typical shopper. “It’s like a used-car lot where you have four used-car businesses on the lot and they perpetuate business. If you only have one, people don’t come.”

Such arrangements, the shopkeeper believes, are becoming increasingly common — hence the pop-up trend. “I talk to all my vendors at the shows. They’ve had a real hard time in this economy. A lot of them are hurting and going under. They’re seeing that people are coming up and going, ‘Do you want to merge? Do you want to do this, do you want to do that? People are getting creative.”

Ms. Warren can sympathize with her new roommate, since she too has had to move: her store was on the Upper East Side for three decades until a rent hike prompted its journey downtown. Her old clientele, she said, tells her that the Upper East Side is becoming increasingly sterile.

East Villagers, of course, worry the same will happen with their neighborhood. “It’s a shame because we just got down here,” said Ms. Warren, “but I keep hearing it’s the last neighborhood to go.”

Marjory Warren, 309 East Ninth Street (near Second Ave.); (212) 876-9777

Musu, same address; (212) 673-5057