Hikari Kohinata gets ready for her first day at school, checking things off as she goes in the manner of a diving preparation checklist: preparation, setting, time, atmosphere, and action. While waiting at the bus stop she compulsively blows her diving whistle.
Another woman joins her on the bus, Mato Katori, who is annoyed that Hikari has sat in her usual seat at the front of the bus, and continues to be annoyed as Hikari sticks her head out the window like an exciteable dog. Noticing Hikari is about to press the bus-stopping button, Mato intercepts and presses it first so that Hikari doesn't get the satisfation. Getting off the bus at the same destination, they start a foot race down the street, in which Hikari manages to jump ahead until Mato jumps onto the back of friend's motorcycle. Mato smiles to herself, thinking she had won, until Hikari appears doing a death-defying leap from the street above.
Alarmed, Mato jumps off her friend's bike to make sure Hikari is ok. As her whistle was in her mouth, Hikari's answer was a bit hard to hear, but the teacher spoke anyways, saying that using the 'step-in method' from that height was very astounding. Hikari agreed, saying that the 'surface conditions' weren't very good. From those terms, the two of them realise that the other was a diver. The woman made a hand sign for 'Are you okay?', and Hikari made a hand sign saying, 'I'm okay'. The two immediately hugged, recognising a kindred spirit in one another, and when they separated, the woman comments that things have gotten very interesting.