Ryuki was just browsing the internet when he encountered a medical condition.
This medical condition was about a woman who absorbed all water that fell on her, and it made milk in her boobs.
Ryuki was curious and wanted to meet such a woman, so he used his gift to find such a woman.
He was stunned that he found such a woman in his apartment.
Now that he had found such a woman, he thought of making her his woman. So, he asked his gift a way to make this woman his girlfriend.
[Wait for some days when Yumika and Hiruki officially become a couple and love each other dearly, and get bored of their daily sex, then appear in front of them and try to hit on Hiruki]
Ryuki looked at it, and he tilted his head. After some asking and getting more understanding, he knew what he had to do.
So, Yumika, the girl who had this medical condition, was into girls, while Hiruki, her current girlfriend, was bisexual.