Have you ever heard of CNCF’s DevStats? It is a tool that tracks and quantifies all contribution activities within CNCF projects by pulling data from GitHub. Using this data, we can analyze ongoing development in CNCF projects from multiple perspectives.
One of the key metrics is “Contribution,” which measures activities such as reviews, comments, commits, issues, and pull requests. This allows us to obtain a quantitative measure of the amount of work being done on a project. We can also break down these contributions by country or by individual.
In this post, we examine the 2025 DevStats data for Japan, focusing particularly on individual achievements. Let’s take a look back at the impact Japanese engineers made over the past year.
Comparing with 2024
We ran a similar report last year and shared it on our blog. Since this is our second year doing this, let’s start with a quick overview of how things have changed.
Note
- DevStats is continually refining its methods as data grow, so please keep in mind that there may be slight discrepancies when comparing year-over-year.
The projects receiving the most Japanese contributions haven’t changed much, which shows that our community’s areas of interest remain consistent. Across all CNCF projects, the total number of Japanese contributors was 40. Last year we had over 50, so unfortunately, the number of contributors from Japan is on a slight downward trend.
Also, looking at the overall Top 20, the scores aren’t as extreme as they were last year. For example, while the top two contributors last year had scores of 8,798 and 7,831, this year’s leaders have scores of 6,463 and 6,176. While the absolute numbers at the very top have cooled off, we see a much larger group of people in the 500 to 1,000 range. This suggests a shift toward a more sustainable structure in which projects are supported by a broader team of consistent contributors rather than by a few standout individuals.
Top 10 contributors in CNCF projects
Here are the top contributors for the five CNCF Graduated projects that have the most Japanese participants. We have highlighted up to 10 people per project based on their contribution scores.
Note
- Except for Kubernetes, these scores cover the project’s entire GitHub organization.
- Company names are based on cncf/gitdm and may not always reflect current roles.
Kubernetes
Kubernetes involves many activities that aren’t strictly code, such as translations. Because of this, we have separated the data into two categories: the main kubernetes/kubernetes repository and the entire organization.
The kubernetes/kubernetes repository remains the most popular among Japanese contributors, with 36 contributors. sanposhiho has shown incredible influence here, reaching a combined score of over 1,000 across their entries*1.
| Rank | GitHub login | Company | Number |
|---|---|---|---|
| 1 | sanposhiho | Tetrate.io | 590 |
| 2 | sanposhiho | Independent | 466 |
| 3 | toVersus | 3-shake | 223 |
| 4 | utam0k | Preferred Networks Inc. | 201 |
| 5 | sunya-ch | International Business Machines Corporation | 143 |
| 6 | everpeace | LY Corporation | 127 |
| 7 | AkihiroSuda | NTT Corporation | 114 |
| 8 | mochizuki875 | NTT DATA | 109 |
| 9 | tenzen-y | Independent | 105 |
*1: These are likely listed separately because of a change in company affiliation during the year.
Kubernetes organization (overall)
Looking at the organization as a whole, tenzen-y took the top spot with a remarkable score, just as they did last year. While the scores at the very top have leveled off in 2025, the “middle class” of contributors is becoming more prominent. This move toward a broader base of support is one of the most interesting trends of the year.
| Rank | GitHub login | Company | Number |
|---|---|---|---|
| 1 | tenzen-y | Independent | 4939 |
| 2 | sanposhiho | Tetrate.io | 1122 |
| 3 | sivchari | Independent | 789 |
| 4 | sanposhiho | Independent | 748 |
| 5 | Okabe-Junya | University of Tsukuba | 716 |
| 6 | shu-mutou | NEC Corporation | 642 |
| 7 | t-inu | Independent | 537 |
| 8 | sunya-ch | International Business Machines Corporation | 346 |
| 9 | everpeace | LY Corporation | 335 |
| 10 | AkihiroSuda | NTT Corporation | 287 |
fluentd
Fluentd continues to be a project where Japanese presence is felt most strongly. Last year, we saw several people break the 1,000-point mark, and that momentum continued into 2025. daipom, kenhys, and cosmo0920 all maintained high scores between 1,000 and 1,500. This is a field where Japan’s long-term commitment is very stable.
| Rank | GitHub login | Company | Number |
|---|---|---|---|
| 1 | daipom | Independent | 1653 |
| 2 | kenhys | Independent | 1392 |
| 3 | cosmo0920 | ClearCode | 1079 |
| 4 | sue445 | Pixiv | 18 |
| 5 | simukappu | Amazon | 13 |
Containerd
In 2024, akihirosuda set a world-class record with a score of 4,392. While that number settled to 2,991 in 2025, he remains the undisputed leader in this space. Japan’s influence on containerd remains massive.
| Rank | GitHub login | Company | Number |
|---|---|---|---|
| 1 | akihirosuda | NTT Corporation | 2991 |
| 2 | haytok | Amazon | 121 |
| 3 | yylt | 114 | |
| 4 | utam0k | Preferred Networks Inc. | 13 |
Cilium
Cilium saw a lot of excitement in 2024 right after its graduation, and we saw several Japanese names in the rankings. In 2025, that work has continued steadily, led by yutarohayakawa and ysksuzuki. While the explosive growth in scores has calmed down, it feels like the project has moved into a more mature phase of deep, specialized involvement.
| Rank | GitHub login | Company | Number |
|---|---|---|---|
| 1 | yutarohayakawa | Isovalent | 513 |
| 2 | ysksuzuki | Isovalent | 282 |
| 3 | shun159 | Amazon | 59 |
| 4 | kahirokunn | Craftsman Software Inc. | 13 |
Envoy
Japanese contributions to Envoy increased substantially in 2025, reaching nearly 400 points and earning it a spot in our report. We are seeing more engineers who work across multiple projects, such as Kubernetes, Cilium, and Envoy, particularly in the network and runtime layers. This versatility is becoming a hallmark of Japanese contributors.
| Rank | GitHub login | Company | Number |
|---|---|---|---|
| 1 | kkk777-7 | CyberAgent Inc. | 264 |
| 2 | anuraaga | Independent | 44 |
| 3 | sanposhiho | Tetrate.io | 31 |
| 4 | shikugawa | Tetrate.io | 21 |
Overall top 20 in CNCF
Finally, here are the top 20 Japanese contributors across the entire CNCF ecosystem.
| Rank | GitHub login | Company | Number |
|---|---|---|---|
| 1 | tenzen-y | Independent | 6463 |
| 2 | akihirosuda | NTT Corporation | 6176 |
| 3 | khanhtc1202 | — | 1519 |
| 4 | daipom | Independent | 1427 |
| 5 | kenhys | Independent | 1248 |
| 6 | sanposhiho | Tetrate.io | 1142 |
| 7 | cosmo0920 | ClearCode | 1025 |
| 8 | sivchari | Independent | 1017 |
| 9 | okabe-junya | University of Tsukuba | 944 |
| 10 | utam0k | Preferred Networks Inc. | 911 |
| 11 | ffjlabo | AbemaTV | 887 |
| 12 | sanposhiho | Independent | 750 |
| 13 | shu-mutou | NEC Corporation | 642 |
| 14 | tnorimat | Hitachi Ltd. | 578 |
| 15 | yu-croco | — | 570 |
| 16 | t-inu | Independent | 540 |
| 17 | kahirokunn | Craftsman Software Inc. | 538 |
| 18 | yutarohayakawa | Isovalent | 513 |
| 19 | anuraaga | Independent | 463 |
| 20 | sunya-ch | International Business Machines Corporation | 433 |
Wrapping up
Building on the first set of data from 2024, this second year of reporting has allowed us to see how the landscape is shifting. While the number of contributors has declined slightly, the core community is becoming stronger and more diverse.
The upcoming KubeCon + CloudNativeCon Japan will be a huge boost for everyone. Hosting this event locally will support our current contributors and provide an opportunity for newcomers to get involved.
Every small act, whether it’s a code review, fixing a typo in documentation, or commenting on an issue, is a real contribution. We look forward to seeing even more names on this list next year as Japan’s presence in the cloud-native ecosystem continues to grow.