During a fight, Happosai uses a scroll to banish Ranma to face a reaper. The next thing Ranma knows, he is on the planet Therum, standing before Liara T'Soni, who has accidentally trapped herself in a force field.
The publication date here is speculative. It was certainly published by 2014-02-28.
Ranma is banished by Happosai to face a reaper. and he happens to find and rescue Liara from the cell on therum