Kagura: Now, if we accept that Santa doesn't exist -- do reindeer exist? Tomo: [after a bout of explosive laughter] This girl believes in reindeer! [Continues laughing, the other girls gasp.] Yomi: Reindeer do exist.
There's no way that kind of flying animal could exist!Luffy!You called?Haha... What are you saying? Reindeer are fictional animals, right? 架空 can mean "aerial" or "fictional", so I don't know if there's some type of pun going on here.