10,000+
Peak Total Monthly Units
Amazon Japan · Case Study #2 · Drugstore Category
Zero Ad Sales to 8,238 Monthly Ad Units (and back down again)
This case study demonstrates the rapid growth that a known brand can have on Amazon Japan, but also highlights how critical inventory management is to longterm success.
Scorecard
Peak Month Data (November 2025)
8,202
Peak Ad-Attributed Units
34.5%
Core Keyword CVR
5.81
Core Keyword ROAS
Project Objectives
Commercially disciplined growth in a structurally constrained operating model.
01
Rebuild listings and storefront first
The starting assets were very basic: simple titles, weak images, and virtually no bullet content. There was no A+ content and no Brand Store page. The first phase was to fully rebuild listing and storefront foundations before launching any ad campaigns.
02
Launch first-ever ad program
After the content foundation was fixed, the next objective was to launch a structured ad program from zero ad history and scale with commercial discipline on a lower-ticket product.
03
Scale inside 1P vendor constraints
Inventory flow, pricing stability, and Amazon purchase-order behaviour sat outside direct brand control via a distributor-managed vendor setup.
Context
What made this account different
This was not a typical seller model where ad performance can scale simply by increasing bids or broadening coverage. The account operated through a distributor-controlled 1P vendor relationship with Amazon Japan, creating structural dependencies outside day-to-day campaign management.
Before we launched advertising, the product was already selling roughly 2,000-3,000 units per month. This was not a demand-creation problem. It was a control-and-conversion problem: improve listing and storefront quality, launch ads with discipline, and build ranking momentum without sacrificing economics.
The key was not just spending more. The key was aligning content, search strategy, and retail fundamentals tightly enough to translate existing brand pull into category-level velocity.
Execution
What we changed and how growth was built
We rebuilt listing content to improve conversion quality, developed a cleaner Brand Store path, and launched the first structured ad architecture in late May 2025. Early spend was focused on high-intent terms most likely to convert, rather than broad low-efficiency coverage.
Performance acceleration became clear from late October into November 2025. At peak, ad-attributed units reached 8,202 in one month and total monthly units moved above 10,000, driving the account to #1 Best Seller status before later slipping when vendor-side constraints tightened.
Baseline Before Ads
2,000-3,000
Monthly units before late May 2025 ad launch
Peak Month
10,000+
Total monthly units at peak velocity
Best Seller Position
#1
Reached in mouthwash subcategory
Keyword Performance
One core term carried major non-branded volume
Best Seller Rank movement reinforced the commercial impact of the campaign ramp. As advertising delivery opened up and sales velocity increased, the account climbed to #1 in the Mouthwash sub-category (earning the Best Seller badge) and moved from 2,000+ to 260 in the main Drugstore category.
Best Seller Rank (BSR) Impact
This illustrates how the right Amazon Japan advertising strategy can amplify an already-known brand's organic base and accelerate rank gains at category level.
Before
Peak
Listing-level proof: from 3,000+ monthly purchases before the program to 10,000+ monthly purchases at peak with the Best Seller badge achieved.
A single core category keyword delivered 34.5% conversion rate, ROAS of 5.81, and a substantial share of non-branded ad orders. That concentration only happens when brand trust, listing quality, and keyword intent are properly aligned.
Core keyword CVR
34.5% conversion on a high-volume category term, indicating strong intent fit and listing relevance.
Core keyword ROAS
5.81 ROAS over the measured period, despite category pressure and price sensitivity.
Sales contribution
This single term accounted for a large share of non-branded ad sales, materially driving ranking momentum.
Operational Reality
Why growth slowed after peak
Advertising unit sales from late May 2025 onward show how strongly performance was tied to ad visibility. Through most of the period, delivery was constrained. Then in late October and through November 2025, Amazon lifted the advertising cap and daily ad-attributed sales scaled rapidly to a peak of 431 units in a single day.
Daily Ad-Attributed Unit Sales
Peak scaling occurred when Amazon lifted spend constraints in late October-November 2025.
Daily Ad Spend and Amazon-Imposed Caps
This spend profile shows distinct ceiling levels, confirming ad delivery was constrained by account-level caps rather than pure demand dynamics.
The ceiling was operational, not demand-led. Amazon Purchase Orders (POs), and the distributor's ability to fulfill those POs inside a 1P vendor setup, meant Amazon did not carry enough inventory to sustain that sales velocity.
As a result, Amazon reduced ad spend to around 3,000 per day, which stalled campaign momentum. In March 2026 the cap was lifted slightly, but delivery remains constrained while Amazon rebuilds stock confidence against current run-rate demand.
This is a common constraint in Amazon 1P models, and it can become more complex when the vendor relationship is managed through a distributor.
Case Study #2 Summary
An established brand with no prior Amazon ads reached category leadership quickly once content, storefront, and advertising were aligned. The ceiling appeared when operating-model control did not keep pace with demand.
10,000+
Peak Total Units
November 2025
late May 2025
First Ads Launch
Built from zero ad history
8,202
Peak Ad Units
November 2025
#1
Best Seller Badge
Reached before vendor constraints
Case Study #2 is based on native Amazon Japan account data and platform screenshots.