I'm not Rumiko Takahashi so I don't own Urusei Yatsura. It seems to me like this story isn't really going anywhere, but that's because I have a certain way in mind to end it and I'm not sure how to get it there just yet.
Lum was walking the streets of Tomobiki doing some window-shopping with Benten keeping her company. "So where's your lech of a boy now?" Benten asked the oni while sampling an earth candy bar.
"Oh, he's with Daddy now, talking about something. Some kind of guy talk, I think." Lum answered as she looked for something to wear. Her pregnancy was advanced enough now that she was starting to show but you couldn't really notice it unless you were trying to. Still, she thought it was a good idea to find something to hide her stomach for a while, since her trademark bikini would easily give her condition way soon.
"Didn't your father say that if you didn't have a ring next time he saw Ataru he'd maim him?" Benten asked.
"Daddy's an oni, not an ogre."
"In Japan there's no difference."
"Are you insulting me?" Lum asked, frowning and sparking a little, experiencing a small mood swing.
"Watch yourself or you could hurt something precious and vulnerable." Benten warned her friend.
Lum immediately calmed down. "Thanks Benten." The biker alien took another bite of her candy. "Y'know, I'm getting hungry because of that. What do you say we go get a beef bowl before we continue?"
"I'd say the blockhead is rubbing off on you if you're craving that." Benten commented. "It's a good thing your kid's gonna be a girl, or it might've gotten a lot of his traits."
Lum would have replied, but some shouts could be heard from down the street and they caught her attention. Very quick both alien women saw the familiar and unwelcome sight of Rei, in all his tiger-cow glory. And he was charging like a bull seeing red. People rushed to get out of his way and it looked like Ran was running behind him trying to catch up.
Lum instantly feared that Rei was coming for her and tried to fly away. As soon as she did though, Rei plowed right into her, sending her soaring down the road and right into a noodle cart. Seeing this, Rei morphed back to his true form and rushed to her, or at least tried to until Benten got in front of him with a gun pointed at him.
"WHAT THE HELL ARE YOU DOING?" The biker alien shouted.
"Lum. Trouble. Indecent." The male oni answered in his typical fashion.
Ran now caught up and looked out of breath. "Sorry... 'pant'. I told him... 'pant'... about Lum and... 'pant'... Darling. He... 'pant'... got upset."
"Why would you tell him? Of course he'd be upset!" Benten yelled at the redhead.
"I thought he'd be happy for Lum." Ran defended herself in her angry Ran voice. Then she switched into Ran-chan mode and voice. "Oh no, is Lum okay?"
Benten turned to see Lum, but kept her gun out if Rei did anything funny. Lum was lying on the pavement and grasping her stomach, grimacing in pain. Benten immediately panicked and got close to the oni. "Lum! Are you hurt?"
"Yes! It's cramping. I need help!" She answered.
Fearing the worst, Benten pulled out a communicator and dialed up Lum's father. "Mr. Invader, get a ship here right now! Lum's been hurt by food-for-brains Rei here and her child's in potential danger. Make it snappy." She then hung up and turned to Rei. "You're going to be turned into a rug for this, idiot!"
Rei looked like he was about to transform so he could run away much quicker. However, Ran grabbed his face and planted a kiss on his lips. In no time Rei became an old oni. "There. That could keep you out of trouble for awhile." She then looked at Benten. "I'll take care of him. Make sure Lum's taken care of." She then led Rei away back to her UFO.
It didn't even take two minutes for a UFO equivalent of an ambulance to show up where Benten and Lum were. Two onis came out and gathered up a still hurt Lum and Benten went inside with her. So far there wasn't any bleeding so she wasn't miscarrying yet, but there was the potential for that. No questions asked, the UFO went back up into space and towards Lum's father's UFO.