Urabe and Tsubaki do their usual routine at their usual place, and as Tsubaki opens his eyes he realizes it's started snowing. They notice the snow is heavy and coming down hard, and they might end up doing their routine in the snow the next day. The two part ways for the day and Urabe opens up her umbrella.
Walking through the Kazamidai shopping district, Urabe is surprised to find Tsubaki's sister, Youko, walking alongside a man. As the two part ways, Youko begins to walk in Urabe's direction and notices her. She grabs Urabe's arm and dashes off, pulling her along. Youko stops to catch her breath, looks at Urabe, and crouches down and starts to cry. Alarmed, Urabe asks what's wrong. Youko is embarrassed and says she can't go home in such a state. Still teary-eyed, she asks Urabe if she'll take a bath with her.
Outside a public bathhouse, Urabe is surprised and says she had no idea there was one in Kazamidai. Youko pulls her inside and pays for them both. As Youko lets her hair loose and begins to undress, Urabe thinks about the weird situation she's found herself in. As she puts her school uniform in a locker, Youko pulls it out and smells it, and says it smells like her high school days.
In the bath Urabe asks Youko asks about the man she was with. She explains it was someone she went to high school with, and Urabe recalls her mentioning him before, and how they parted ways when he went to college in Kansai. Youko says she bumped into him today while he was visiting family, and they just had a conversation, but it made her really emotional. Youko tells Urabe he was the first boy she ever dated and that makes him special. She remembers that Urabe said she has someone she likes, and tells her she should treasure that feeling. Urabe mumbles "maybe I'll just tell her..." and Youko asks her if she just said something. Blushing, Urabe tells her she's dating Tsubaki. Youko jolts up onto her feet in shock as Urabe does the opposite and sinks down further into the bath.
Youko makes sure Urabe is telling the truth and realizes Urabe had come to their house several times. She asks Urabe if they've kissed yet, Urabe tells her they haven't, and also tells her Tsubaki is the first person she's dated, just like the man Youko was with earlier. Youko gets on her knees and asks Urabe to be good to Tsubaki, and bows into the water. Embarrassed again, Urabe suddenly stands up and bows in return, asking Youko to be good to her, too.
Urabe and Youko leave the bathhouse to find a substantial layer of snow covering everything outside. The two of them part ways and shortly after Youko is found by Tsubaki who came out with umbrellas to find her since she is late coming home. They find an empty lot now covered in snow, Tsubaki says it reminds him of Youko, and recounts a snowy morning when they were younger. Youko had brought him to the lot to play and made sure she was the first one to leave a footprint in the pure white snow. Youko looks at Tsubaki and remembers what Urabe said in the bath. Blushing, she thinks to herself "will the first one to leave his footprint on her... be my brother?" before suddenly shoving him face-first into the snow. He asks her what she did that for and, smiling, she says "you'll be the first boy to leave a footprint, so you'd better straighten up!" much to Tsubaki's confusion.