One morning when Jun woke up, her body was that of a grown woman. Arashi was the only one that noticed right away, though none of the others knew who she was. To get out of an awkward moment, she tells the others she is the older sister of Jun, by the name of Ryoko. When approaching Kaya to tell her the truth, Jun learns that they are planning a surprise birthday party for her. Jun ends up helping the preparations for the party. While helping the preparations, Hajime compliments on how beautiful she is, but Jun gets annoyed as the older Jun is being compared to the younger Jun.
どういうわけか、自分が大人の身体に成長してしまっていた潤。とりあえずカヤに相談しようと方舟に向かうが、目の前のスタイルの良い女性が成長した潤だと気付いたのはあらしだけで、他の面々は誰一人として気付かない。そんな中、一に女だと知られたくない潤は、とっさに姉の涼子だと名乗ってごまかすが…。
