Martlet

After Clover gave their SOUL up for the better of Monsterkind, the underground, specifically Martlet and her friends would remain in a better place, forever remembering Clover's sacrifice. When the seventh human, Frisk, fell, they would spare everyone they'd encounter, eventually confronting ASGORE. As he was interrupted by Toriel, and soon every of Frisk's friends, Flowey would take advantage of this and steal everyone's SOULS. Flowey, who sreverted to being Asriel, the God of Hyperdeath, and Frisk, the child who still managed to SAVE him. Asriel used his power to returned everyone's SOULS back to their bodies, along with the fallen humans, even Clover. Of course, at the cost of Flowey becoming... well, Flowey and SOULess again. Sans, Alphys, and Frisk, however, would confront eachother about the amalgamates. Specifically... The last one. Kanako. Sans, however, would stay behind, leaving Frisk and Alphys to the work. Alphys and Frisk would contact Martlet about this, bringing her along too. With that, they'd face many challenges, but would reunite with Kanako. Thus, breaking the news to Starlo and the Feisty Five... Who, took it pretty well, and eventually, having Kanako reunite with Ceroba at long last. Now, they would all return to the surface, along with Martlet who sat with Frisk. Martlet questioned their actions. Frisk told her to look behind them. Martlet did, and there stood Clover, alive. Martlet, of course, was overjoyed to see them.

Context: Chujin is Ceroba's deceased husband. After he started experimenting and injecting himself with the previous fallen human - Integrity, His SOUL would deteriorate. Before he died, Chujin requested Ceroba see the tapes he created about his studies, and to continue his legacy, which involved creating a serum that could turn anyone into a boss monster. Kanako, Ceroba's young daughter would overhear and watch the tapes, convincing her to inject her with it so they could save the underground. It wouldn't work, causing her to fall down. Ceroba would send her to the lab in Hotland to hopefully revive her, but never got a response back. To make a working serum - she'd need a pure human SOUL, which happened to be Clover's after not killing anyone. She'd lead them to the Steamworks, then to Hotland, but was stopped by Starlo and his posse, The Feisty Five, consisting of Ace, Mooch, Ed, and Moray. Starlo would confront Ceroba about the tapes, but she would flee. Martlet would conclude by going to the Ketsukane mansion to see it theirselves, and they did. Martlet and Clover would meet up with Ceroba, battling. After being defeated by Clover, Martlet and Starlo would comfort her, then turn their attention back to Clover. Martlet and Starlo wanted to argue, but Ceroba saw there was no way to hide them here. Clover, who responded by giving up their SOUL.