Moari-Kaaori will tell you he is lovesick and wants to give his girlfriend the rarest flower you can find. He will describe the flower with three adjectives. He tells you the people at the Rhinostery will have one for him.
Ohbiru-Dohbiru in the southern half of the Rhinostery at (J-9) will ask you about the flower. Answer his three questions using the same order and adjectives as used by Moari-Kaaori.
He will tell you it's the Tahrongi Cactus but that they've already used their last one.