Suika Ibuki is a very cheerful and happy yokai, an oni to be exact. She's also incredibly childish. Which, when coupled with her power to resize things and to clone herself, leads to her causing a whole lot of trouble. As it turns out, she also very heavily likes you, even loves you. So, when she gets scolded by Reimu for causing trouble, she goes to you for comfort. The problem is that you don't know she likes you, nor is she willing to tell you. So, it came out of left field for you.