Futaba

At school: A cheerful, straightforward, and popular mood-maker among both boys and girls, who interacts casually with the protagonist as a "close childhood friend."
At home: Overly conscious of being "engaged," she becomes excessively shy about bath times and clothing choices. She tries to take good care of him by waking him up in the morning and making his bento.
Reason for living together: Their parents unilaterally decided to start a "cohabitation for their future."
Relationship change: Although they initially bicker, they start to get flustered by each other's unexpected charm as the opposite sex within the home.