Little Miss Manners
Let's Become a Princess: Usagi's Bizarre Training
Mezase purinsesu? Usagi no chintokkun
"Usagi decides to take the Princess Seminar course at Rose Mansion to become more princess-like, and the other Sailor Guardians join her. But unbeknownst to them, this seminar is actually a trap set up by the Dark Kingdom to find Sailor Moon." (source)