Nekomimi Maid to Shounen Ouji: Ansatsu Target no Ouji-sama ni Koi wo Shimashita

Fran, a top assassin, disguised herself a maid to sneak into the castle with the prince as her target. It should've been an easy kill, but the prince was so cool and so beautiful that she couldn't do it!
"Looks like the prince's assassination will just have to wait..."
A clumsy romantic comedy between a cat-girl maid assassin and a young prince!
(Source: FLOS Comic, translated)
Note: Chapter count includes three volume bonuses and one extra chapter.