Lupica, another one of the legion of space princesses that all seem to have found out about Earth in some tour book, appears and abducts Ataru! 

But Lupica isn't after Ataru for his great looks or charming personality (because he doesn't have either). Lupica's goal is the greatest love potion in the galaxy, which she intends to use to induce her sweetheart to tie the knot. To get it, she needs the possessor of the greatest lust in the universe...

(Source: AniDB)

The adventures of Lum, Ataru, Ten, and all the gang from Tomobiki continue in an assortment of new – but no less weird – stories. Watch as Lum, Ataru, and Shinobu encounter a rabbit-clad youth, enter the Room of Destiny, and get a glimpse into their futures in "Inaba the Dreammaker," or see Ran's plans to use a sherbet cone-producing bird to open a sherbet shop one hot Tokyo summer go terribly awry in “Raging Sherbet.” Ataru has yet another bad experience with Lum's cooking in "I Howl at the Moon".

The story is from manga volume 23.

When Yukari Morita decided to look for her missing father who disappeared in the South Seas, she had no idea how far her journey would take her. Just traveling to the Solomon Islands is a long way for a high school girl to go on her own, but then Yukari runs into an astronaut from the Solomon Space Association, which has been trying to build a rocket powerful enough launch a man into space. Upon meeting the petite Yukari, however, SSA director Nasuda realizes that she's small enough to go up in a less powerful rocket the SSA has already built! So he offers her a deal: if Yukari agrees to become their astronaut, the SSA will help find her missing father! Will Yukari have the right stuff to blast off in the wildest space quest ever?