In a shocking development for Momota and Orihara-san, it turned out that the woman Momota's father is dating is actually Orihara-san's older sister, Kisaki! What's more, she now knows about Momota's real age and that they've been lying to her! She tells them to break up immediately, saying it's for their sake. However, rather than fall apart, the bond between Momota and Orihara-san grows stronger than ever, and they refuse her. Now what lies in store for their relationship? Will Momota's family have his back? What's the bombshell that Kisaki-san drops on them? And why did Orihara-san invite Momota to a hotel to be alone together?! Find out all this and more in the fifth volume of this sugary sweet romcom about a couple with a slight age gap!