iri Writes Her First Anime Song for a Terminally Ill Heroine
The opening theme is the headline here. iri is a Japanese singer-songwriter who has never written for an anime before, and according to a report from Japanese entertainment news site Oricon News, she composed "Period" with the show's heroine in mind.
In her comment, iri said she was struck by Satoko, a character who is nearly crushed by a reality she wants to look away from, yet stands her ground and pushes straight ahead anyway. She added that the song came at a personal turning point for her, and that she wrote it while layering her own present feelings onto Satoko's.
Manga author Oreco Tachibana (橘オレコ) also weighed in. Tachibana described the track as carrying an urgent wish, the feeling of not wanting to give up and reaching out to grab hold of something, along with a strong will to keep moving forward no matter the situation. Tachibana said listening to it makes the story and the characters' feelings surface more vividly.
The ending theme is "Yumegokochi" by TOOBOE.
What the Main Trailer Shows
The new trailer, posted to Fuji TV's official anime channel, is built around the fateful first meeting between Satoko and Shinpei, two people who were never supposed to cross paths. It includes Shinpei's blunt confession to her, which translates roughly as "My love's a little heavy, but I'll make you happy." That line has served as the series' tagline since the first teaser.
From there the trailer moves into the turbulent developments that sweep both characters up, as Oricon puts it. The outlet frames the central question as where the forbidden romance between a killer whose obsession deepens the more he loves and a young woman with little time left will finally land.
Firefly Wedding is set in the Meiji era, as Japan modernizes. Satoko Kirigaya is the daughter of a noble house who dreams of marrying into a prestigious family to make her father proud, and she is dying. Shinpei Gotō is the assassin who dotes on her. Oricon bills it as a twisted love story where mystery and obsession intersect, and the manga has passed 4.5 million copies in circulation.
The Cast and Crew Behind the Adaptation
Lynn voices Satoko, and Kōki Uchiyama (Tomura Shigaraki in My Hero Academia, Toge Inumaki in Jujutsu Kaisen) voices Shinpei. Kent Itō plays Kōtarō Ogawa and Kenjirō Tsuda plays Mitsueda.
The series is animated at david production (JoJo's Bizarre Adventure, Fire Force), with Takahiro Kamei directing. Yūko Kakihara handles series composition and scripts, Yukiko Aikei is the character designer, and NOGRID composes the score.
Tachibana is also the author of Promise Cinderella and provided the original character designs for the TV anime Nazotoki wa Dinner no Ato de. Firefly Wedding is published in Japan by Shogakukan, with the 12th collected volume out in June 2026.
Looking Ahead
Firefly Wedding premieres October 9, 2026, on Fuji TV, airing Fridays at 11:30 pm in the network's Noitamina block. Crunchyroll has confirmed it will stream the series as it airs.
Viz Media publishes the manga in English for readers who want to get ahead of the anime. No release date has been announced yet for iri's "Period" as a single.