After a successful trip to Mazela where his products quickly became the talk of the town, Shiro returns to Ninoritch with the intention of slipping back into his usual routine at the store. Cue his two younger sisters turning up on his doorstep to throw his life into disarray by announcing they plan to stay at his house for a while. Unsurprisingly, it doesn't take the twins long to find the portal to another world in the closet. Keen on exploring, they set out into the forest on the other side with Shiro, who tags along to make sure his fearless sisters don't meet an untimely demise. All's fine and well—until one of the girls finds a mysterious giant egg and insists on taking it with her. Just what kind of egg is it? And how will the siblings deal with whatever hatches out of it? More to the point, will Shiro be able to cope with his two high school-aged sisters running around and causing mayhem in his adopted second home?