Figuratively speaking, 99 times out of 100, it's "the male's fault" (facepalm). But in this case, Senpai fell for her junior and (ahem) gave her Approval that he may (ahem, again) meet her needs whenever her 'horny' switch gets flipped ... the lucky bastard.
"You can't take back what you've done"?
Well yeah, I mean he already stuck it in and took her first time. But hey, things turned out perfectly alright with Sweet Vanilla and he also apologised at the end.
So, the perfect technique to getting your Senpai to notice you is to just stare at her endlessly every morning until she comes to like it, and stops wearing panties?