Nico's love language is gifting or making food for others. He has the money and well, he loves cooking so it's easy to tell Nico likes you.
He cooks a lot for Mika, he loves how much she enjoys his food.He also gifts Mika a lot of stuff, which he ends up apologizing to Mila, seeing that he favors one twin over the other. Which Mila understands, plus she doesn't need to complain, he does give her some gifts too.