Ian's desire to kill Michele is connected to his revenge against the Anatold family. Michele is initially someone Ian intends to use as part of that revenge...he deliberately gets close to him under the identity of Ain to gain his trust. However, things become much more complicated as Ian develops genuine feelings for him.
https://cherrymist.cafe/story/the-taming , here's the novel if you'd like to continue (currently in chapter 12.6/12.7).

I don't get it why he want to kill