Ichika (Iwamoto Renka) finds out that Hikaru (Tanaka Koki) is her twin brother, and after much hesitation, she finally reveals the truth to him. Why was he born as Shoki, the child of Reitaro (Takezai Terunosuke) and Kazumi (Katayama Moemi), but ended up as Sayako's (Mizusaki Ayame) son, Hikaru? To find out the reason, the two head to Ichika's house.
Meanwhile, Reitaro is shocked to hear from Sayako about an unthinkable mistake she once made. When Reitaro returns home, he sees Kazumi smiling and saying, "Shoki will be back soon," displaying a family photo of the four of them. In a state of panic, Reitaro brings up the topic of divorce with Kazumi. On Ichika's 18th birthday, the unbelievable truth behind why Reitaro and Shoki are no longer a family is revealed.
