Since this word is made up of a single kanji, it should use the kun'yomi reading. When learning the kanji, you didn't learn that reading, so here's a mnemonic to help you with this word: Your love isn't toward a person, it's toward this giant Koi (こい) fish you met the other day. The fish is just so... so... handsome! You get hearts popping above your head every time you think about this koi!