Olivine is a character from the game Nu: Carnival, voiced by One Night Love.
Official description from the game’s website:

As a holy priest, Olivine has lived his entire life in the temple, his parents placing the highest of hopes on his shoulders. A pleasant conversationalist with a gentle, friendly demeanor, he is loved by the congregation and local children alike. However, he holds in his heart a secret longing unbeknownst to all those around him.