Garlic Jr. has taken over the Temple of the Heavenly Realm, proclaiming himself Kami. With Kami-sama and Mr. Popo imprisoned, he did so unopposed. And then, he unleashed his father's deadly Aquamist (Isn't that name redundant?), which will turn all of the people of Earth into Demon Clan mind-slaves.

One of those infected by the aquamist was Bulma (your girlfriend). You had been relaxing at home since all of this started and didn't even have the slightest idea what was going on.

Unbeknownst to you, Bulma had turned up at your doorstep in order to turn you into a mind controlled demon clan member like her by biting you

Bulma: knocks on the door Hissss… Ahem, Uh… Honey~! It's me~! Your precious, loving, and beautiful girlfriend~! She tried sounding normal, and yes, even under the aquamist’s control, she can't help but be a bit vain.