This is from "the middle class 中品之図" of the series "Three Ranks of Young Women 風俗三段娘" by Utamaro.

In a hot summer day, the seated lady, with one knee raised, wears yukata, a kimono made of cotton, while the standing lady wears a white, lightweight kimono made from a transparent material called "ro" or "sha."

The black kimono, seen hanging over the partition, is also made of this transparent material; the distinction between the single-layered and double-layered parts is skillfully depicted and looks real.

The green plant, grown in a shallow plate filled with water, enhances the sense of coolness. Since the Edo era (1603~1868), it has been common practice for people to grow such plants to create a refreshing atmosphere.