Mato Katori says goodbye to her class on their first day of school, and informs them that at Yumegaoka High School participating in school clubs is mandatory so to take some time to think about what club they'd like to join. Futaba Ooki is disheartened, but Hikari Kohinata is absolutely thrilled. Futaba muses to herself that she'd hoped she could just go home at the end of school for the rest of high school. She is momentarily distracted by cherry blossoms floating by the open door, and when she looks up, she notices Hikari running in the opposite direction to the school exit.
Curious, Futaba gets up and follows her to see where she's going, only to get dragged along by Hikari to the diving club's meeting room. Hikari barges straight in, but Futaba is anxious that the diving club might feel intruded by them barging in so she peeps around the door, only to find the room is empty apart from diving equipment and Hikari sat on a chair playing with Cha. Hikari wrongfully deduces that since Cha is the only one here, he must be the diving club's advisor.
Hikari notices Futaba admiring the diving suits, so she explains that there are two kinds of diving suits: wetsuits which allow water into the suit, and drysuits which are waterproof. Futaba asks how the suits can be waterproof, but Hikari insists its easier to just demonstrate and puts on one of the diving club's drysuits. Hikari explains that wetsuits are used on warm days, and dry suits when it's cold - drysuits hold a layer of air between your body and the water, which helps insulate the diver and stop them losing energy through heat loss.
Hikari convinces Futaba to also try on a dry suit. Futaba is hesitant, but tells herself that it's ok just for a little while. The two then sneak into the school's pool - Hikari gleefully dives in, which causes Futaba to panic until she sees that Hikari is floating. Futaba wonders to herself why she's allowed Hikari to convince her to do all these things she'd normally be too scared to do, but reasons that Hikari's cheerfulness is what's lifting her spirit. Futaba dives into the pool. The two float together, and Hikari notes that while floating in the water you can only hear your breathing, until little by little the sound melts into the water and eventually, you can't tell your body apart from the water. Hikari asks if Futaba would like to dive with her. Futaba wonders for a moment before smiling, and tells Hikari that she'll consider it.