Kazuya Yanagiba is the human identity of the Senior angel, Limone. He is put in charge of watching over the Love angels.
Approximately over 100 years ago he met the previous incarnation of Angel Lily. The two instantly fell in love with each other. However, their relationship was short lived due to Lily's fate. Lily's death deeply scarred him. Later in the anime when he remembers who he is (being the Angel Limone), both him and Yuri (Angel Lily) resumed their relationship and start dating.
On Earth as his human form Kazuya Yanagiba (or dear Yanagiba-san, a nickname that Momoko, Yuri and Hinagiku like to call him) has no idea that he is the Angel Limone. Whenever the Love angels are in danger Queen Aphrodite calls for him to seek their aid. That is when he changes into his true form, the Angel known as Limone.