The protagonist, Yasuhira Sasamoto, was looking forward to his father's one-month business trip overseas.
The timing of the trip was fortunate — it started right after summer vacation began.
He thought spending summer vacation abroad would be a valuable experience.
However, as the vacation approached, he became increasingly anxious about language barriers, cultural differences, and safety concerns.
Eventually, he grew so nervous that he threw a tantrum and declared he didn't want to go at all.

At that time, the Makabe family — neighbors with whom they had a close familial relationship — offered to take Yasuhira in during his father’s absence.
Mitsuya "Obasan" (Auntie), who loved him like her own child.
Yuzuki "Oneechan" (Big Sister), who always treated him so kindly.
As Yasuhira begins living under the same roof as them, a faintly sweet, rosy aroma fills the air...
What will become of Yasuhira when faced with the crisis of losing control — both mentally and physically!?