Episode 9 of "Glass Heart" kicks off with a serene scene at Naoki's countryside abode, where Akane and Naoki are immersed in creating music together, their harmonious collaboration filling the air. Meanwhile, back at the studio, Sho and Kazushi receive a text from Naoki, announcing the completion of their latest track.
The following morning, Akane awakens to a startling sight—Naoki lies unconscious on the floor, surrounded by several sheets of music, each bearing the title "Glass Heart." Elsewhere, Isagi toils relentlessly on preparations for the upcoming festival.
A nostalgic flashback unveils Isagi laboring over a track, to which Naoki offers his approval before proceeding to make a multitude of transformative adjustments. Isagi's awe at Naoki's talent is palpable. Later, in a haze of intoxication, Isagi makes a fateful phone call, instructing someone to release the track under his name alone, omitting Naoki's credit.
Cutting to the rock music festival, Isagi attempts to justify his actions to Naoki, claiming he only wanted the best for him. Naoki, however, rejects his excuses and storms onto the stage. The haunting memory of that day still lingers heavily on Isagi.
Naoki finds himself hospitalized, with his doctor posing a poignant question to Sho: Will Naoki sacrifice his life for his music, or will he abandon it to live? Akane, filled with guilt, apologizes to her teammates for absconding with Naoki. Sho persists in his belief that Tenblank's era has come to a close, leaving Akane distressed and fleeing the scene. Kazushi chases after her, only to be bidding farewell by a resolute Akane.
Sho's path eventually crosses with Kai, who has caught wind of Tenblank's troubles. She propositions him, requesting to return as Akane's manager. Kai astutely points out that Sho's anger stems from his jealousy over Akane's deeper understanding of Naoki.
A nostalgic flashback unfolds, depicting Naoki persuading Sho to join his ranks by playing him a melody meticulously composed just for him. Presently, Sho, seated comfortably in his car, finally presses play on the new track Naoki had sent. To his astonishment, he discovers Naoki standing outside, gazing in through the window. Naoki, with earnest eyes, declares his desire for Sho to be his sole guitarist, a role Sho readily embraces for life's duration.
Kazushi stumbles upon an enigmatic empty folder named "New B" within the file Naoki had shared. Curiosity piqued, he navigates to the same file on Naoki's audio setup and starts to listen. Caught red-handed, Naoki informs him sternly that this composition was never meant for prying ears.
As the festive season of Christmas draws near, Akane finds herself delivering curry for her mother's eatery once more. Her mother tasks her with taking an order to Naoki's residence, but Akane declines, holding firm to her decision to quit Tenblank. Enter Kazushi at the restaurant, attempting to coax her back. She stands her ground, teasing that she might just elope with Naoki again. Kazushi then hands her Naoki's latest creation, confessing that he thought he loved her, but what he truly cherishes is her drumming prowess.
A memory flashback reveals Kazushi confessing to Naoki that his hidden new song was inspired by Akane, explaining his reluctance to share it with anyone else. In the present, Naoki reaches out to Akane, seeking a favor. He unveils the tune he penned during her slumber at the countryside retreat. Realizing Naoki is standing amidst the snowflakes, Akane dashes out to find him as he begins to serenade the air with his new song. The lyrics strike her heart; they declare his undying love for her.
Upon locating him, Naoki apologizes for his earlier deceit, confessing his inability to fall in love was a lie. He avows his affection for every facet of her being. As his melody concludes, their lips meet in a tender kiss. Back at the studio, Sho offers solace to a dejected Kazushi.
When Akane and Naoki return, they find Sho and Kazushi have meticulously prepared everything for their upcoming practice session. Tenblank is reborn!
Elsewhere, Isagi finds himself engrossed in a live stream hosted by Yukino, who reveals a stunning truth: all her compositions were actually penned by Naoki, not Isagi. This bombshell sets off a chain reaction, casting a dark cloud over the onset of Isagi’s rock festival. Artists, one by one, begin to withdraw from the event, their enthusiasm dampened by the revelation. The audience, too, starts to disperse, the festive atmosphere wilting like a wilting flower.
Just as hope seems to fade, a fleet of Tenblank buses rolls up to the scene, bringing with them a sudden twist. Kai’s announcement, it transpires, has summoned the loyal Tenblank fans to the festival, infusing it with a new sense of purpose. She exudes an air of determination, hinting at her eagerness to reclaim her role as the band’s manager. And then, amidst thunderous applause, the band members themselves make a grand entrance, their presence igniting the crowd with renewed excitement and energy.
