Security Engineer Intern
Mercari
Security Engineer Intern
Mercari
Peer-to-peer mobile marketplace for secondhand goods
Mercari, inc. · Minato City, Japan (Hybrid) · Temporary · Posted 2026-04-27
Workplace: hybrid
Department: Mercari HD
Employment Status: Intern
Please apply only if you are able to stay in Japan, as the internship must be from within Japan.
Regarding the arrangement of airline tickets, this applies only to those who have not purchased tickets at the time of the internship offer.
Work Hours: Able to work more than 20 hours per week 2-3 months of Internship is encouraged.
Circulate all forms of value to unleash the potential in all people
"What can I do to help society thrive with the finite resources we have?" The Mercari marketplace app was born in 2013 out of this thought by our founder Shintaro Yamada as he traveled the world. We believe that by circulating all forms of value, not just physical things and money, we can create opportunities for anyone to realize their dreams and contribute to society and the people around them. Mercari aims to use technology to connect people all over the world and create a world where anyone can unleash their potential. For more information about Mercari Group’s mission, see Mercari’s Culture Doc.
https://careers.mercari.com/en/culture/
This internship provides an environment where you can engage in experience design with a management perspective, not just engineering tasks, and grow into a leader who will drive the Mercari Group in the future. For students aiming to become future product leaders, this internship offers the opportunity to take on challenges from both business growth and social problem-solving perspectives.
Mercari Engineering Principles
Mercari Engineering Principles are a shared understanding that serves as the foundation of engineering beliefs and behavior at Mercari. The Engineering Principles are designed to complement the organizational identity (Mercari’s mission, values, and culture) from an engineering viewpoint.
These principles ultimately help us achieve Mercari’s mission by defining the ideal state we seek to realize in the long term.
For more details, please see the following link:
As an Intern in the Mercari Security Engineering Team, you will have the opportunity to participate in security design, process reviews as well as develop and deploy security countermeasures, and execute penetration tests. This is a unique role within Mercari since you will be involved in high-stakes projects across the organization. The candidate will be exposed to the following topics, and will be invited to work on one opportunity of his/her choice:
See here for more information about our mission and values.
https://careers.mercari.com/en/culture/
Threat Detection and Response Team
This team develops and operates Mercari Group’s security monitoring, detection engineering, and incident response capabilities. Our work spans security logging, detection-as-code, SOAR automation, AI-assisted workflows, and hands-on investigations to support fast and scalable threat monitoring across the Group.
Platform Security Team
This team develops and operates the security controls and guardrails that protect Mercari's global engineering platform, covering access management (GitHub, GCP, PAM), CI/CD and infrastructure-as-code security, supply chain risk management, and Kubernetes security. By partnering closely with Enterprise Security, Product Security, AI Security, and Infrastructure teams, the team embeds security into the software development lifecycle so engineers across the Group can build and deploy safely at scale.
Product Security Team
This team is responsible for ensuring that all customer-facing and internal -facing applications are built securely throughout the entire development lifecycle, preventing vulnerabilities before products reach production. This is achieved by conducting threat modeling, security architecture reviews, automated scanning, and penetration testing, while working directly alongside engineering teams to remediate flaws. Additionally, the team establishes secure coding standards, manage vulnerability disclosure programs, and build automated security guardrails so developers can ship features quickly without compromising safety.
Enterprise Security Team
This team develops and operates scalable security controls and guardrails to protect Mercari’s global workforce platform across identity, endpoints, core SaaS, and corporate networks. By embedding Zero Trust and defense-in-depth principles, the team minimizes security risks while delivering a secure-by-default experience that boosts productivity and enables fearless innovation across the Group.
A Culture of Innovation: We’re experimenting with AI-driven development, zero trust architecture, and secure-by-design initiatives—and interns are encouraged to contribute, ask questions, and grow.
Mentorship & Collaboration: You’ll be guided by experienced security engineers who are passionate about sharing knowledge and building the next generation of talent.
Required Experience/Skills
Shared understanding and belief in our company’s mission and values
Foundational knowledge of SQL and data querying
Preferred Experience/Skills
Basic understanding or strong interest in any of the following:
Experience attending or speaking at domestic and international security conferences, such as SECCON, Hardening Project, Black Hat, or DEF CON.
Leveraging AI for security operations automation and the protection of AI-driven systems
Basic experience with software development tools such as Git, dependency management, build and deployment tools
Understanding of modern Web or mobile applications
Language
English or Japanese: Independent (CEFR-B2)
The Security Team is a globally diverse group, with members from many different countries and a wide range of Japanese and English proficiency levels. We value mutual respect, effort, and empathy, and we actively work to bridge language gaps so that every team member feels welcomed and understood—regardless of their native language. Our goal is to create a supportive and inclusive environment where everyone can thrive and collaborate effectively.
For details about CEFR, see here.
https://careers.mercari.com/en/language/
At Mercari Group, we value empathizing with and embodying the mission and values of the Group and each company. To promote the creation of an organization that maximizes the total amount of value exhibited by all members, we would like to understand the experience and skills of each candidate as accurately as possible.
Hiring Process at Mercari Group
Learn more about our recruiting process here.
Here at Mercari, we work to realize a world in which no one’s potential is limited by their background and everyone has the opportunity to freely create value. We also firmly believe that a mindset of Inclusion & Diversity is essential for us to achieve our mission.
This, of course, extends to our hiring practices as well. Mercari is committed to eliminating discrimination based on age, gender, sexual orientation, race, religion, physical disability, and other such factors so that anyone who shares our mission and values can join us, regardless of their background. For more details, please read our I&D statement.
https://about.mercari.com/en/inclusion-diversity/
Please read and acknowledge our Privacy Policy prior to submitting your application.
https://careers.mercari.com/en/privacy/
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Mercari operates a mobile peer-to-peer marketplace for buying and selling secondhand goods. Users list items by taking photos in the app, and buyers complete purchases there, with payments held in escrow until receipt is confirmed. Revenue comes from seller fees (10% in Japan; 10% plus 3.6% buyer protection in the US), plus Merpay payments and promoted listings, plus shipping partnerships for integrated delivery. The platform differentiates itself through a simple mobile experience, escrow and buyer protection, shipping integration, and a broader marketplace including Mercari Shops for sellers, with a goal of extending product life and supporting a circular economy.
Explore more opportunities at Mercari