The Tool You Need 'After' Sedori Scouter: Catching New Mercari Listings in 1 Second [2026 Edition]
Even if you can instantly determine Amazon profits with Sedori Scouter, 'noticing the moment that item appears' on Mercari or flea market apps is a different problem. Profit calculation and discovering new listings are actually completely different phases of work.
In this article, I will explain how to bridge the 'few-second delay' in Mercari sourcing that users of Sedori Scouter-type profit judgment tools encounter next.
Sedori Scouter tells you 'if it's profitable.' But it doesn't tell you 'when it appeared.'
Research tools like Sedori Scouter and Keepa instantly determine market prices, rankings, and profit margins. These are essential for sourcing decisions.
However, these are basically tools for determining 'whether the item in front of you is profitable.' The more popular a profitable item on Mercari or Rakuma is, the more likely it will be SOLD within seconds to minutes of being listed. Have you ever had the experience of realizing 'this is profitable' with Sedori Scouter, only to find it's already been bought?
In other words, Mercari sourcing requires two different capabilities.
Discovery: Noticing the moment a new listing meeting your criteria appears (Speed)
Judgment: Determining if it is a profitable item (The domain of Sedori Scouter)
Many people have tools for 'judgment' but are doing 'discovery' through manual monitoring searches. This is the bottleneck.
3 Conditions for Automating 'Discovery'
Official Mercari notifications are convenient, but due to their specifications, there is inevitably a delay of several minutes. Popular items disappear within those few minutes. To systematize discovery, you need the following three things:
Short monitoring intervals (fetching new listings in seconds, not minutes)
Precise condition filtering (picking up only what you want and filtering out noise)
Immediate awareness (receiving notifications on your smartphone even when you're not in front of your PC)
If you can satisfy these three, you can create a state where 'you have the product page open before your rivals, even before you judge it with Sedori Scouter.'
FleaMa Hunter: A Tool Dedicated to 'Discovery'
The desktop application I develop and provide, 'FleaMa Hunter,' specializes in exactly this 'discovery.' It does not replace the 'profit judgment' of Sedori Scouter, but acts as a partner that fills the gap before that, 'noticing the moment it appears'.
Monitors new Mercari listings at 1-second intervals and notifies you immediately when an item matching your criteria appears
LINE / Discord / Slack notifications allow you to stay aware even when you are out
Supports Boolean search (AND / OR / NOT) and regular expressions. Enables precise filtering such as 'Nike AND 27.5, excluding junk' or 'collecting variations in model numbers all at once'
Exclude keywords, excluded sellers, and price range specifications to effectively reduce noise notifications
Detection results can be exported to CSV, allowing you to analyze which conditions were effective later
Unlike free notification apps or custom-made scripts, we continuously maintain the tool to adapt to changes in the flea market site's specifications, minimizing the risk of it 'suddenly stopping to work one day.' If you have improved the accuracy of your profit judgment with Sedori Scouter, it is now time to increase your discovery speed.
Try it for free for 7 days first
The best way to see if 'notifications will really be faster for your sourcing genre' is to actually run it and check. You can start FleaMa Hunter with a 7-day free trial.
▶ Apply for a free trial of FleaMa Hunter
Get products you know are 'profitable' from Sedori Scouter before your rivals do. Let's use a system to capture those 'first few seconds.'
→ If you would like to compare it including differences with other monitoring tools, please also check out the 'Thorough Comparison of Mercari Monitoring and Notification Tools'.