Shinobu could be described as petite and wide-eyed school girl. Very thoughtful, pensive and often full of melancholy. Shinobu is usually very sweet and kind, that is until you cross her. Like Lum, Shinobu has quite a jealous streak and a quick temper. Mostly Shinobu really has a tendency to over-react to every little thing and go into a conniption fit whenever things get too weird. Anytime Shinobu becomes angry, frightened or excited, she gains infinite strength. She then goes into a screaming berserker rage, most often throwing desks and other types of furniture. This power stems from her jealousy of Lum when she was going out with Ataru. But it stuck with her long after she lost all romantic interest in him. This strength is one example of how Lum's presence effects Tomobiki. Thanks to Lum, Shinobu is one of the most physically powerful characters in Urusei Yatsura.

Shinobu is really a sweet girl, but she has just about the worst luck in the world with men.

At the very beginning Shinobu was Ataru's girlfriend. Ataru and Shinobu had been together since they were kids. She stuck by him, despite his horrible behaviour.

Early on in the series, Shinobu finally begins to lose interest in Ataru. There are mainly three reasons for this. She got tired of Ataru constantly jilting her, Lum was constantly causing aggravation for Shinobu, but mostly because Shuutarou Mendou came along. Shinobu was immediately captivated by this suave and handsome rich boy. Throughout the whole series Shinobu persues Mendou's love but with only moderate success. It's obvious that Mendou has some feelings for her, but Shinobu knows that he wants Lum more. It takes her a while, but soon Shinobu gets over Mendou since she begins to see how Mendou isn't much different from Ataru. Even after all that Shinobu still likes Ataru and Mendou, but only as friends.

As Shinobu searches for love it starts to look like the only guys who have any interest in her are weirdos.

Near the end of the series when Shinobu loses all hope along comes a bumbling but kind-hearted young man in a rabbit costume named Inaba. He loved her from the moment he met her and soon Shinobu began to fall for the earnest young man.