Citizen Tsuyosa vs G-Shock CasiOak
The classy one and the sporty one
Quick Verdict
The Citizen Tsuyosa ($250–$500) is a 40mm steel automatic with a sapphire crystal and an integrated bracelet — the dressier of the two by a wide margin. The G-Shock GA-B2100 CasiOak ($100–$150) is solar-powered, Bluetooth-connected and rated to 200m in a carbon-reinforced resin case. Tsuyosa if you want it to look like jewellery; CasiOak if you want to stop thinking about it.
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Specifications Compared
| Feature | Citizen Tsuyosa Automatic | Casio G-Shock GA-B2100 CasiOak |
|---|---|---|
| Price | $250–$500 | $100–$150 |
| Case Size | 40mm | 45.4mm (48.5mm lug-to-lug, 11.9mm thick) |
| Movement | Automatic Caliber 8210 | Quartz Module 5689 (Tough Solar + Bluetooth) |
| Caliber Type | Citizen/Miyota In-House Automatic | Casio Quartz (Solar-Powered) |
| Power Reserve | 40 Hours | About 7 months on a full charge without light; about 18 months in power-saving (Casio) |
| Water Resistance | 50m (5 ATM) | 200m (20 ATM) |
| Crystal | Sapphire Crystal with Cyclops | Mineral Glass |
| Case Material | Stainless Steel | Carbon Core Guard Resin |
| Origin | Made in Japan | Made in Japan |
Category-by-Category Analysis
Design & Aesthetics
Steel and sapphire against octagonal resin
The Tsuyosa is a steel watch with an integrated bracelet and a sapphire crystal with a cyclops over the date — a look that leans deliberately upmarket. The CasiOak takes the octagonal bezel silhouette and renders it in carbon core guard resin, which is why it costs a fraction as much and weighs a fraction as much. They are aimed at the same shape and completely different intentions.
Movement & Performance
Mechanical charm against solar quartz with more functions
The Tsuyosa runs Citizen automatic Caliber 8210 with a 40-hour power reserve and a date. The CasiOak runs Casio quartz module 5611 with Tough Solar and Bluetooth, adding world time, a stopwatch, a timer and an alarm. On capability and on the absence of upkeep the CasiOak is straightforwardly ahead — it charges from light and sets itself from your phone. The Tsuyosa answers with a rotor and a sweep, which is the entire reason people buy mechanical watches.
Wearability & Fit
Smaller and heavier versus larger and lighter
The Tsuyosa is 40mm in stainless steel, so it is the smaller watch but carries real weight on the wrist. The CasiOak is 44.4mm but built from resin, so it is the larger watch and the lighter one by a long way. Which is more comfortable depends entirely on whether you would rather feel the watch or forget it.
Value & Cost of Ownership
CasiOak costs less and asks less
The CasiOak sits in the $100–$150 band against the Tsuyosa in $250–$500, and it is the more robust watch of the two: 200m against 50m, and solar power instead of a mechanical movement that will eventually want servicing. The Tsuyosa answers with sapphire, which resists scratches far better than the CasiOak mineral glass. Cheaper to buy and cheaper to keep is the CasiOak; nicer to own is the Tsuyosa.
Brand Heritage
Both Japanese, both punching above their price
Both are made in Japan and both are among the most talked-about watches their makers have released recently. The Tsuyosa put an integrated-bracelet steel automatic within reach of a first-time buyer. The CasiOak did the same thing for the G-Shock line by giving it a shape people wanted to wear with a shirt. Neither is a downmarket version of anything.
Materials Face-Off
| Component | Citizen Tsuyosa Automatic | Casio G-Shock GA-B2100 CasiOak |
|---|---|---|
| Case alloy | Stainless steel 316L. | Casio's proprietary monocoque case technology integrating carbon fibers into fine resin. The carbon fibers dramatically raise the tensile strength and modulus of elasticity of the case structure, allowing the GA-2100 to achieve an 11.8mm thickness — the thinnest analog G-Shock at launch — while maintaining full 10m drop impact resistance. Total case weight: 51g. |
| Sapphire crystal | Verneuil-grown synthetic corundum, Mohs 9. Anti-reflective coating, single side. Mohs 9 | Flat mineral glass with Mohs hardness ~6. Thermally tempered for impact resistance — flexes under force rather than shattering like sapphire. Not scratch-proof, but replacement crystals cost ~$10. |
| Lume specification | Super-LumiNova on the hands and markers. The application is light - this is not a watch to rely on for low-light legibility. Grade and glow duration are not published by the manufacturer for this reference, so neither is claimed here. | Durable urethane polymer resistant to sweat, saltwater, UV radiation, and skin oils. Features quick-release spring bars. Known to last 5–10 years with daily wear before degradation. |
| Bracelet alloy | Stainless steel 316L matching the case. | Secured by 4 Phillips screws for 200m (20 ATM) water resistance. The GA-B2100 is Tough Solar: a rechargeable cell topped up by any light, so there is no coin cell to swap. Casio rates a full charge at about seven months of normal use without light, and about eighteen months in power-saving. |
| Premium Lineage: Cobarion® & DAT55G Titanium (MRG-B2100) | — | The luxury MRG-B2100 variant ($3,500+), hand-assembled at Yamagata Casio's Premium Production Line (PPL) by certified "Medalist" craftsmen, uses Cobarion® (cobalt-chromium alloy, 4× harder than pure titanium) bezels and DAT55G titanium (3× harder than pure titanium) bracelet links. |
Cost of Ownership Compared
Who Should Pick Which
Pick the Citizen Tsuyosa Automatic if…
- Budget-conscious buyers wanting serious quality under $500
- Those who prioritize scratch resistance — sapphire crystal
Pick the Casio G-Shock GA-B2100 CasiOak if…
- Anyone wanting an indestructible daily beater under $100 with serious design credibility
- Water sports enthusiasts — 200m WR with G-Shock shockproofing
- Watch modding enthusiasts — massive aftermarket ecosystem of metal conversion kits
- High-end collectors needing a dedicated beater alongside their luxury pieces
Citizen Tsuyosa Automatic
- No hacking seconds. When you pull the crown to set the time, the seconds hand continues running. Setting precisely to-the-second is impossible. The single most-cited Tsuyosa complaint.
- Unidirectional rotor. Only winds in one direction; reserves take longer to build than bidirectional movements.
- Modest accuracy spec. ±10 to +25 sec/day in practice is the realistic band; significantly worse than the Tissot Powermatic 80.
- Proprietary endlinks. Limited strap-swap options.
Casio G-Shock GA-B2100 CasiOak
- Stealth-black legibility deficit: The GA2100-1A1 has absolutely no Neobrite luminescent paint on hands or indices. Low-light readability is poor — you must rely entirely on the Double LED Super Illuminator.
- Mineral glass scratches: Not sapphire. Daily beater use will accumulate minor scuffs over time. Replacement crystals are cheap (~$10) but require caseback removal.
- Tiny digital subdisplay: The LCD window at 4:30 is small and genuinely difficult to read for anyone with less than perfect vision. The Hand-Shift feature (sweeps hands to 7:35 position to clear the LCD) helps but isn't a substitute for a full digital display.
- Module 5689 is quartz: For mechanical-watch purists, this is a non-starter. For everyone else, it's a feature — better accuracy (±15 sec/month), no winding, no expensive servicing, and solar charging that never needs a battery change.
Our Verdict
Citizen
Tsuyosa Automatic
Choose the Tsuyosa if you want something that reads as a proper steel watch. It is 40mm, it has an integrated bracelet and a sapphire crystal, and it runs a mechanical automatic — the whole appeal is that it looks and feels like far more money than it costs. Accept the 50m rating, which means splashes and hand-washing rather than swimming.
Check Price on AmazonCasio
G-Shock GA-B2100 CasiOak
Choose the CasiOak if durability and indifference are the point. Solar power means no battery to change, 200m means water is a non-issue, and the carbon core guard resin case is built to be knocked about. It is bigger at 44.4mm, and mineral glass will mark where sapphire would not, but nothing else here asks so little of you.
Check Price on AmazonThe Bottom Line
The Citizen Tsuyosa NJ0150 is a 40mm stainless steel automatic with a sapphire crystal and 50m water resistance, while the Casio G-Shock GA-B2100 CasiOak is a 44.4mm solar-powered quartz in carbon core guard resin rated to 200m — the Tsuyosa is the dress-leaning choice and the CasiOak is the durable one.
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How This Page Was Made
Our comparisons are generated from a hand-maintained specification database and reviewed under our editorial standards. We use AI tools to assemble pages from that data. We don’t invent specs: every number traces back to the database, and when we correct an entry, the fix is applied site-wide. As an Amazon Associate, The Horologist earns from qualifying purchases.