Yea apparently taking Futaba’s v-card didn’t quite fulfill the requirement. So it either has to be from a specific someone, or like you said “by force” (or it wasn’t about virginity at all but I doubt it).
I just hope that this won’t be about Yumi and Sensei won’t experience another massive fast forward to the future that brings him directly to his deadline (though I am 9/10 sure that he will miss the bar for whatever reason)
Futaba lost her virginity in the first update of Chapter 3, Sensei didn't get the command until two updates later.
And it's not just anyone's virginity, because NIki would have qualified.
So it's either someone specific (liekly Yasu, the initial messenger, or Sana, who has clearly been chosen for something), or the force element is at play.
But I do expect that he will not meet the deadline, and that the consequences for that failure will be what push us into Chapter 4 and very likely, a much darker Winter.