User blog comment:B214/General discussion/@comment-24098614-20170819203739/@comment-29963364-20170820005809

Stella's parents don't know that she and Ikki had sex already.

There was even a scene where Stella's old school friends teased Ikki by asking "how far he got with Stella," and then Lunaeyes (Stella's older sister) stepped in and said "there's no way that they would do something so irresponsible/improper."

Ikki laughed nervously, but no one figured it out. At least not yet.