My Days with the Demoness

After his best friend died, college student Asaki Tomohiro dropped out of life — became a NEET, stopped engaging with most things, and poured his energy into building a portal to another world. He finished a prototype. He tested it. The accident that resulted pulled a girl out of another dimension entirely: Nero Ei Vixonni, a demon lord's daughter who is furious about being here and refuses to owe anything to a human. The prototype is broken, trapping Nero in Asaki's world. He has promised to fix it in one and a half months. In the meantime, Nero has decided she will help fix his miserable life since he is fixing her problem. What follows from this arrangement is not what either of them expected.