She makes her first appearance when she and her team, Song Dynasty Vase, are asked to fight against the Team Try Fighters in a practice match. She berates Fumina at first, telling her to say thank you for coming to face her club.
During the battle she and her team use a Jet Stream attack to take out Sekai but Fumina and Yuuma use their own combination; when Fumina looks cornered, Yuuma snipes one of her allies through a small gap in a mountain. With one their allies down, her remaining team member retreats to the ocean where she is distracted by Sekai emerging with a Soten Guren-Ken, giving Hoshino a clear view to take her down and leaving Kaoruko to fight the Team Try Fighters on her own. Driven to desperation, she launches a powerful volley at the Powered GM Cardigan, which Yuuma is unable to intercept. However, Sekai interrupts again with a Senpu Tatsumaki-Geri, blowing away all of her missiles and following up with a dropkick that sends her R-Gyagya crashing into the ground. He then tries to finish her off with a Seiken-Zuki to try and crush her Gunpla with immense strength. Though the Gunpla and shield hold up, the ground below her caves in, blowing a large hole through the colony and opening up a vacuum that threatened to suck in her machine. However, Sekai saves her Gunpla from falling while holding up her shield. She asks why he saved her, which he responds that it was because she really she loves Gunpla and that the shield she cherishes is "awesome". She asks for his name and he replies, she willingly forfeits the match with a smile on her face, enamored by his kindness and skill.
The next day, she waits for Sekai and offers him a lunch box, having developed romantic feelings for him. Sekai happily accepts her gift despite being clueless as to why she is giving it to him, causing Fumina, Yuuma and Mirai to groan at his ignorance.
- Both Kaoruko and her brothers share the same Japanese voice actress in Gundam Build Fighters Try and Gundam Build Fighters respectively.