YUIMETAL: "The Fall"

A theory of BABYMETAL’s Evolution. The incident that became a catalyst.

This essay separates publicly documented events from clearly labeled speculation. It is written as an analytical exploration of BABYMETAL’s structural evolution, not as a statement of medical fact.

Phase 1: The Incident and the Hidden Struggle (2014–2017)
Fact (March 1, 2014): During the Budokan "Red Night" show, YUIMETAL falls from a 1.5-meter walkway during "Headbangeeeeerrrrr!!!!". She was off-stage for several minutes while SU-METAL and MOAMETAL continued, visibly shaken. She returns for the final song but is visibly less mobile.

Speculation: The fall caused a chronic spinal or lower back injury. Instead of a full stop, the "Idol" culture of "the show must go on" led YUIMETAL to perform through pain for years.

Fact (Late 2017): During the Five Fox Festival and Big Fox Festival, fans document a rectangular protrusion under YUIMETAL’s costume. This did not appear on SU-METAL or MOAMETAL’s costumes, leading to the conclusion that she was wearing a medical back support or brace. They also report that YUIMETAL appears to have a "puffy" face.

Speculation: If YUIMETAL was dealing with a chronic back injury or a related inflammatory condition, she likely would have been on medication to manage the pain enough to perform, which explains the physical change. The "puffy face" was Moon Face, a clinical side-effect of high-dose corticosteroids (like Prednisone) used to manage chronic inflammation so she could continue to tour. During the 2015-2016 period, YUIMETAL still performed at a high level, but the Five Fox Festival is where the “stiffness” became undeniable.

Phase 2: The Hiatus and The Choice (2018)
Fact (Dec 2017 – Oct 2018): Just hours before the massive Legend S: Baptism XX show in Hiroshima, it was announced YUIMETAL would miss the show due to "illness." YUIMETAL misses the Legend S shows and remains absent for the 2018 tour. When the World Tour began in Kansas City, YUIMETAL was absent without any prior warning from management, causing a massive fan outcry (#WhereIsYui). In October, she officially resigned. YUIMETAL stated that while she had hoped to return, her "physical condition is not at its best" and she wanted to pursue a solo career as Mizuno Yui.

Speculation: The decision to not immediately replace YUIMETAL with a permanent third member was a tactical move by Koba-metal and Amuse. By keeping the spot "open", they left a door open for a miracle recovery while avoiding a fan backlash that would have occurred if they "replaced" an icon like YUIMETAL too quickly. Her official departure letter mentioned her "strong desire to return" but that her "physical condition" wouldn't allow it. This supports the theory that they held the spot open for nearly a year by this point purely because she was trying to recover.

Phase 3: The Avengers and the "Sealing" (2019–2022)
Fact (June 2019): At Yokohama Arena, the "Avengers" system is introduced. Three dancers (Riho Sayashi, Kano Fujihira, and Momoko Okazaki) rotate as the third member. They are never named, never sing, and never have the same face mics that MOAMETAL or YUIMETAL are known to have.

Speculation: This "nameless" status served two purposes: it maintained the hierarchy where SU-METAL and MOAMETAL were the only "true" members, and it prevented the audience from bonding too deeply with a replacement, just in case the “Avengers” or another experimental lineup were no longer needed as a semi-permanent fixture of the lineup should YUIMETAL recover and change her mind about pursuing a solo career.

Fact (Oct 2021): BABYMETAL is "sealed" and goes on a total hiatus for over a year.

Speculation: This was a contractual showdown. SU-METAL and MOAMETAL were now adults. As the girls entered their mid-20s, they likely sought more creative input or better terms as their original "Idol" contracts (likely signed when they were children/teens) were expiring. If they didn't sign new "Artist" contracts (moving away from their childhood "Idol" terms), BABYMETAL would likely end.

Phase 4: The "METALVERSE" Backup Plan (Jan 2023)
Fact (Jan 2023): At the BABYMETAL Returns: The Other One show, the "sealed" period ends. During the performance, a "mirror" version of the band appears - three young girls performing as a parallel 2014-era BABYMETAL.

Speculation: This was the Break-Glass-In-Case-Of-Emergency plan. These girls (later known as METALVERSE) were essentially a "Soft Reboot" of the brand if SU-METAL and MOAMETAL had refused to sign in 2022. By introducing them while SU-METAL and MOAMETAL were still there, they "seeded" the idea of a multiverse so fans would accept a replacement lineup if the originals walked away. Amuse could have used the "Lore" (The Fox God, Multiverses) to explain that the original SU-METAL/MOAMETAL/YUIMETAL had ascended, and these new girls were the "New Saviors of Metal" from another dimension. It allowed the brand of BABYMETAL to survive even if the individuals left.
Miko Todaka (the center of METALVERSE) is widely considered the "heir apparent" to SU-METAL. The theory that they were a "Soft Reboot" is highly credible because they didn't just sing any songs at that time, they performed the 2014-era choreography perfectly, essentially proving the "BABYMETAL Brand" could continue with new faces.

Phase 5: Solidarity and the "Metal Forth" Era (2023–2025)
Fact (April 2023): At Black Night, Momoko Okazaki is officially named MOMOMETAL, restoring the group to a permanent trio.

Fact (Summer 2023): The "parallel trio" 2014-era BABYMETAL resurfaces at Summer Sonic but is now officially branded as a separate entity called METALVERSE, eventually expanding to five members.

Fact (2024–2025): The band releases METAL FORTH, featuring their heaviest sound and global collaborations (Electric Callboy, Spiritbox, Polyphia, etc.).

Speculation: MOMOMETAL joining signified that the "Old YUIMETAL" spot was finally closed. With a permanent third member who could not only sing, but also growl, the band was freed from the "trauma" of the duo-years. This stability allowed for the experimental, high-collab sound of METAL FORTH - an album that likely wouldn't exist if MOMOMETAL were still part of the rotating dancers.
With the "Original" brand secured, the "Backup" group was no longer needed as a replacement, so they were spun off into their own experimental project (METALVERSE) to recoup the training investment.

Fact (Sept 30, 2025): Yui Mizuno is officially released from Amuse Inc., choosing to live life as a private citizen.

Speculation: This delay - 7 years after she left the band - suggests that Amuse kept her under a "holding contract." They likely hoped she would eventually produce solo work (as she stated in 2018). Her total exit in 2025 suggest that either her health never reached a point where she could handle the rigors of the industry, or she simply found a new path in life and waited for her final contract to lapse.

YUIMETAL’s injury, while tragic, was the catalyst for the band's survival.
The Vocal Level-Up: Without YUIMETAL leaving, we never get MOMOMETAL. While YUIMETAL was a great performer, Momo’s ability to provide harsh vocals (growls) has fundamentally changed what Koba-metal can write. Songs on METAL FORTH like the Spiritbox and Electric Callboy collabs wouldn't have worked as well with the original "soft" vocal harmony of the YUIMETAL-era.

The Creation of METALVERSE: We now have two "Fox God" bands instead of one. Amuse turned a "replacement plan" into a revenue-generating spin-off.