Episode 3 of "Glass Heart" unfolds with the exhilarating shoot for Crystalline Echo's music video serving as its backdrop. Amidst the buzz and camaraderie, Naoki makes a bold announcement: he yearns for Tenblank to grace the stages of the renowned TV show, Music States. Soon after, the atmosphere shifts as Yukino, another artist shooting at the same studio, pays Naoki a visit. Akane, observing their seemingly close bond, can't help but feel a twinge of surprise. Meanwhile, Kai voices her apprehensions to Sho about the band's TV debut and Naoki's disregard for her opinions.
The following morning, Akane steps into Naoki's music studio, expecting a day of rigorous practice, only to find Kazushi lost in the melody of his solo composition. She learns that practice is off the agenda due to Naoki's scheduled performance with Yukino. Disheartened, Akane heads home to lend a hand at her mother's curry shop, only to discover that her mother has already entrusted the duties to her friend, Eiko.
On the eve of their Music States appearance, Akane ventures to the studio alone, eager to hone her skills. To her astonishment, she encounters Naoki, who reassures her that Tenblank's moment in the spotlight is just around the corner. With a confident smile, he vows that despite the inevitable highs and lows, their band will persevere.
The day arrives, and Tenblank assembles at the Music Stage venue. Isagi's presence there sparks a revealing conversation with Naoki. It transpires that Naoki penned Yukino's song and agreed to perform with her, strategically positioning Tenblank as the evening's closing act. Isagi harbors expectations for Naoki to pen and produce more of Yukino's tracks, but Naoki remains noncommittal.
Just before their rehearsal, disaster strikes as Kazushi realizes their audio tracks have vanished without a trace. The band springs into action, recording new tracks in a mad dash, forcing them to forgo their rehearsal time. Kai instructs Akane to proceed to the makeup rooms aboard a charming boat. On her way, she crosses paths with Yukino, who inquisitively wonders how Akane manages to resist falling for Naoki. Akane stands firm, insisting that her focus remains steadfastly on the music. Her resolve is further tested by a call from Toya, who doubts Tenblank's chances of impressing the audience.
Back in the band's makeshift tent, Kai feels increasingly marginalized as her voice goes unheard. Driven by a mixture of frustration and emotion, she storms off to the makeup boat, only to discover Akane pounding away on the drums in an adjacent room. Overwhelmed by the unspoken synergy between Naoki and Akane, Kai makes an impulsive decision, sliding the lock shut, inadvertently imprisoning Akane within the room.
The band swiftly becomes aware of her absence. As they frantically search for her, the boat housing the makeup rooms glides away from the harbor and sets sail. Akane comprehends the dire situation and cries out for assistance, only to realize with dread that her phone is in an entirely different room. Meanwhile, the concert kicks off with Naoki and Yukino mesmerizing the audience with their latest single. On board the ship, Akane stumbles upon a hidden door within the room, leading her to the vessel's uppermost deck, isolated and helpless. She shouts for help, but the air remains unanswered. Fortunately, a smaller boat approaches, and to her astonishment, aboard it are none other than Naoki, Sho, and Kazushi. They rescue her and, in an unexpected twist, make their grand debut right there on the boat itself! Their captivating performance garners immense praise, and positive reviews pour in across social media platforms. Not long after, the music video for "Crystalline Echo" is released. As the band watches in awe, Akane is taken aback by the realization that she might, after all, be developing feelings for Naoki.
