It's Nothing - S1.E11

To make up for missing the beach, Azusa's parents gets everyone tickets to the pool. Ushio decides to keep her distance from Azusa so Norio's secret won't be found out, which annoys Sumika since she's the only one Azusa knows well. Conveniently, Kiyori separates everyone into two groups based on their breast size, putting Sumika with Ushio and Tomoe. Ushio and Tomoe get hit on by some guys, but Sumika scares them off when they show no interest in her figure. Sumika then gets competitive with Tomoe over her swimming ability, but inevitable loses. After recovering on Ushio's lap, she teaches her how to swim. As they do, they are spotted by Azusa, who realises Sumika has feelings for Ushio and wonders if she was just in the way. She does find a little comfort after talking with Tomoe and decides to write a story based on the two.