She had nothing to be mad about, Reimu had just proposed to her! And instead Reimu found herself sexually assaulted! As if she would let it end there without getting revenge.

"Hey...Reisen." Reimu got her breath back, and was on her knees, crawling close to Reisen. She pushed her nose against the rabbit toward her neck, unconcerned if her warm breath ended up in her ear. She moved Reisen's hair away with her hand before leaning forward to kiss her sensitive neck, to see how she'd react.