かくしん的☆めたまるふぉ～ぜっ！ (Kakushinteki☆Metamaruphose!) is the opening theme for the first season of the anime series Himouto! Umaru-chan (干物妹！うまるちゃん), based on the manga by Sankaku Head. The song was composed and co-arranged by Asuka Ogura alongside arranger manzo, and performed by voice actress Aimi Tanaka in character as the protagonist Umaru Doma. Its title is a characteristic pun, かくしん的 (kakushinteki) can evoke both "revolutionary" (革新的) and "core" (基本的), while めたまるふぉ～ぜっ (metamaruphose) blends "metamorphose" with まる (maru), a playful nod to Umaru's own name. The energetic, bouncy arrangement matches the anime's comedic slice-of-life tone about a seemingly perfect high school girl who transforms into a lazy otaku at home. The track debuted in maimai PiNK at the version's launch on December 9, 2015, as a POPS&ANIME category song. It later received a Re:MASTER chart in maimai MiLK (April 17, 2018) and DX charts at the launch of maimai でらっくす (July 11, 2019). The MASTER chart for the DX version was designed by 小鳥遊さん (Takanashi-san), while the Expert DX chart was handled by サファ太 (Safata), who also designed the Standard Re:MASTER. Other Standard chart designers include Revo@LC (Expert) and mai-Star (Master). The song was removed from Asian maimai DX arcade editions starting with DX Splash PLUS and from Chinese editions starting with 舞萌DX 2021, though it remained available in Japanese cabinets for a period afterward before being delisted on September 16, 2021. Outside of maimai, the song also appears in SEGA's other rhythm game franchises CHUNITHM AIR and オンゲキ.