Jirai-kei Hoikushi-chan ni Honrousaretai!

When Yuki, a high school boy, goes to pick up his cousin from nursery school in the place of his uncle, he finds the nursery school teacher Satomi dressed like a jirai-kei girl. Yuki doesn't know what to think of her, because she seems expressionless most of the time, but then she would smile at him every now and then.

(Source: Number Nine, translated)