Mudako: The Time Capsule of Promises - S1.E46

Mudako remembers that as a human, she and her friend, Nobuko, hid a time capsule, only to find that Nobuko never returned to help her unearth it. Shiori reminds Mudako of their friendship, and, with the Speech Garnet, finds the time capsule with Nobuko's letter. Shiori purelizes Mudako, turning her Akiramestone into an Akiramenaistone, and she reunites with Nobuko.