As the body-switching becomes a regular, albeit unpredictable, part of their lives (happening two or three times a week), Taki and Mitsuha begin to truly "live" as one another.
The Cultural Thread: Musubi
In Itomori, Mitsuha's grandmother, Hitoha, takes Taki (who is in Mitsuha's body) and Yotsuha up the mountain to the family's high-altitude shrine. Along the way, she explains the concept of Musubi (Linking/Binding):
"Tying thread is Musubi. Connecting people is Musubi. The flow of time is Musubi... They represent the flow of time itself. They converge and take shape, they twist, tangle, sometimes unravel, break, and then connect again."
Taki listens, fascinated. They leave an offering of kuchikamizake (the sake Mitsuha made) at the hidden shrine inside a massive collapsed crater. Hitoha drops a hint that chills Taki: she asks, "Mitsuha, you're dreaming right now, aren't you?" It's as if the grandmother knows the soul inside is not her granddaughter's.
The Date in Tokyo
Back in Tokyo, Mitsuha (in Taki's body) has been incredibly busy. She used her charm and emotional intelligence to land Taki a date with his beautiful coworker, Ms. Okudera.
When Taki wakes up back in his own body on the day of the date, he is panicked. He has no idea how to talk to a woman like Okudera. The date is awkward; Taki is stiff and nervous. Eventually, Ms. Okudera realizes his heart isn't in it. She tells him:
"You used to be different. It's like you're searching for someone else today."
The Sudden Silence
After the failed date, Taki tries to call Mitsuha to vent and tell her what happened. For the first time, he realizes he doesn't actually have her phone number—only the diary entries she leaves in his "Notes" app.
He looks up at the sky. The Tiamat Comet is due to pass its closest point to Earth that very night. He expects to switch bodies again the next morning so they can swap stories about the date and the comet.
But the switch never happens.
One day passes. Then two. Then a week. The diary entries on his phone begin to disappear, flickering away into static as if they never existed. Desperate and haunted by a landscape he saw in "his" dreams, Taki decides to find the town of Itomori using only his sketches and memory.
The Shocking Discovery
Taki travels to the Hida region of Japan. After days of searching, he finally finds a local who recognizes his drawings. But the man looks at him with pity and horror.
He leads Taki to a vast, water-filled crater where a town once stood. Taki learns the devastating truth: Itomori was destroyed three years ago when a fragment of the Tiamat Comet broke off and struck the town during a festival.
He checks the records of the deceased. There, among the hundreds of names, he finds her: Mitsuha Miyamizu.