Like someone earlier said, I kinda hope not. I'm kinda tired of the whole incel-bait trope of slutty girl with sad backstory get fixed by loser guy's pure love for her. I'd rather her just enjoy sex, and not find someone worth settling down for yet.
I changed my mind on the Raw. On the bottom-left panel there is a opened condom package, implying that a condom was put on and then Misaki jumped in before her sister.
This is confirmed in the next chapter where the sister says to change the condom.