Umino Nagi was swapped with another child at birth. He’s going to meet his real parents today, but on his way to school, he meets a girl who is threatening to die to get out of her engagement.

Erika joins Nagi’s and Hiro’s morning study sessions to wingman for Nagi, and Hiro wants to come hang out at her place.

The household visits the diner to attend Yohei's birthday party and learn some family secrets surrounding them. The next day after a study session, Erika succumbs to a cold that she caught, and the household, including Hiro, scrambles to help her through it.