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MSJ-121 Demi Trainer [YOASOBI Collaboration Ver.]

A humble school trainer suit dressed up in neon YOASOBI colors, sold as a music single's plastic bonus toy.

MechaGrade Score

3.3/5

Demi Trainer [YOASOBI Collaboration Ver.] · 1/144 · 2022

GradeHG

Scale1/144

Released2022

Runnersn/a

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The verdict

I like this kit a lot more as a curiosity than as a Gunpla purchase on its own merits.

It is the same simple, snap-fit Demi Trainer mold that anchors the early Witch from Mercury HG line, just repainted in neon pink and black for YOASOBI's Blessing CD single, and that base kit is genuinely pleasant to put together. But this is a bundle item first and a model kit second, and I would not point a builder here if the goal is the best possible Demi Trainer on a shelf.

Best for: YOASOBI or Witch from Mercury completionists who want the collab piece, not first-time builders shopping for value

The full review

What it is

The Demi Trainer is Asticassia Technical College's training suit, the humble machine Chuchu pilots in the early episodes of The Witch from Mercury, and Bandai built the HG around that idea: light, simple, cheap to produce. This YOASOBI version takes that same tooling and swaps the school grey and yellow for a striking pink, black, and white scheme with neon marking stickers lifted from the single's cover art. Built up, it looks sharp on a shelf next to the regular release, and there is something charming about a trainer mech getting a pop idol glow up. The proportions are compact and a little blocky in a way that reads as deliberately unglamorous, which fits the suit's in-universe role as a student's first machine.

The catch

This was released bundled with YOASOBI's Blessing CD single and a short novel, priced around 4,400 yen, so you are paying music-collab prices for what is, mechanically, a basic early HG. Color separation leans on stickers rather than molded plastic for a lot of the neon accent work, and the accessory loadout is thin: a stick weapon, a small submachine gun, and a shield, with the fuller gear only showing up if you also buy the separately sold expansion parts set. Panel lines are light and the frame underneath is simple rather than showcase-grade, so detail payoff is modest compared to later kits in the line.

Who it's for

If you are a YOASOBI fan or deep into Witch from Mercury and want the collab piece for what it represents, get it, the novelty and the CD tie-in make it worth owning on those terms. If you just want the best standalone HG Demi Trainer to build and pose, buy the standard release instead and put the difference toward the expansion parts set, which does more for the finished look than the neon stickers do. First-time builders will find the assembly easy and forgiving, but this specific version is a fan-service purchase more than a showcase kit.

The build story

What the build is actually like, and the engineering worth knowing about.

The build itself is straightforward and snap-fit, true to the trainer's role as an entry-point machine in its own show. Gates are simple and the part count is low, so cleanup is quick and there is little risk of frustration even for a first-time builder. The neon marking stickers need patience since misalignment shows on the flat panels, but nothing about the assembly fights you.

The engineering carries over the standard Demi Trainer's tricks: shoulders that extend outward on a small drawer mechanism for wider arm swing, a rotating forearm, a neck that pulls out to open up head and torso posing, and a waist ball joint that lets it tilt forward and back rather than just twist. Knees and elbows bend to roughly ninety degrees, which is enough to hold a decent stance. Weapons are limited to a stick, a compact submachine gun, and a shield, with two interchangeable head options, and the fuller weapon set only comes through the separate expansion parts kit.

Lore & trivia

01The MSJ-121 Demi Trainer is the training mobile suit used by students at Asticassia Technical College in Mobile Suit Gundam: The Witch from Mercury, and it is the machine Chuchu pilots in the show's Earth House unit.
02This YOASOBI Collaboration Ver. was bundled with YOASOBI's Blessing CD single, the opening theme for The Witch from Mercury, released November 9, 2022, alongside a short original novel written by series screenwriter Ichiro Okouchi.
03The set also included YOASOBI collaboration marking stickers designed to work with the separately sold HG 1/144 Gundam Aerial, tying the trainer suit and the show's main Gundam into the same collab release.
04Demi Trainers use a modular Daedalus multi-tool system that swaps standardized block units for different training equipment, from missile launchers to circular saws, reflecting the suit's role as a school tool rather than a combat machine.