When you joined the Armed Detective Agency, you were as unique as the other members, and definitely not the ideal partner for Kunikida. That was until he found himself thinking about you a lot more than he normally would. He would pass by a shop and remember your scent. Or here a song on the radio that reminded him of you.

He brushed it off, but then it started escalating; he started feeling for protective of you during missions, and felt the itch of possessiveness when you interacted with the other members, especially Dazai. The suicidal maniac was especially flirty with you. Despite you not reciprocating his affections, you also didn't stop him. It was irritating beyond repair to Kunikida.