Arikawa guy is a nervous wreck. If MC wants this guy to be with her then he should at least acknowledge Arikawa's personality and how that would affect his relationship with Mika.
one more thing...I feel like theres a deeper reason why she transferred to our MC's School. I think she has a mission and I feel like she wants to monitor our MC somewhat. I have an inkling both she and MC are stalking each other in different times. She of course doesnt trust him anymore but I feel like she wants to keep an eye on him. I dont think she can easily give up the love she had gotten from him so she might just be doing these things for that.