Senior Full-stack Engineer | Osaka or Tokyo / Remote (Flexible) | Multinational Team #224

Company Overview

The company operates a marketing SaaS platform leveraging LINE. As a rapidly growing startup, it utilizes AI technologies to help brands build sustainable and trustworthy relationships with their customers.

In addition to its LINE marketing tools, the company develops and provides a range of services, including LINE 1-to-1 business chat, digital membership card LINE mini apps, and AI-powered call solutions.

■Key Features

• Operates in the C-commerce market, which is estimated to be worth nearly JPY 30 trillion globally and is projected to surpass the e-commerce market in certain countries by 2025
• Achieved 760% business growth over the past three years in the marketing SaaS domain
• Successfully raised a total of JPY 6.3 billion in funding (including JPY 3.5 billion in Series B)
• Ranked No.1 in LINE marketing in Japan
• A global organization with offices overseas and team members representing 20 different nationalities

 

Job Description

Role Overview

You will be responsible for developing the company’s AI-native customer engagement platform. The platform enables businesses to build meaningful relationships with their customers through automated messaging, real-time communication, and AI-powered interactions.

As a Full Stack Lead Engineer, you will lead the design and development of both the front-end and back-end of the platform. Beyond hands-on development, you will provide technical leadership across the team, including defining system architecture, mentoring engineers, improving development and operational processes, and driving technical decision-making.

Working closely with the Product, Design, AI, and Infrastructure teams, your mission will be to deliver a scalable, intuitive, and high-quality customer engagement experience for enterprise customers in Japan and beyond.

 

Key Responsibilities

• Lead the design and development of scalable frontend and backend systems for the product
• Build and enhance customer-facing applications as well as internal operational tools
• Design robust APIs, backend services, and platform integrations
• Drive technical decision-making and contribute to system architecture discussions
• Collaborate closely with Product and Design teams to shape product direction and user experience
• Continuously improve system reliability, scalability, performance, and operational observability
• Develop well-tested, maintainable code following modern engineering best practices
• Establish and improve engineering standards, development workflows, and technical processes
• Mentor engineers through code reviews, technical guidance, and knowledge sharing
• Troubleshoot and resolve complex production issues in distributed systems
• Communicate effectively across cross-functional teams in both Japanese and English
• Take end-to-end ownership from requirements gathering through production deployment and ongoing operation

What You’ll Gain / Why This Role is Exciting

• The opportunity to shape the future of AI-powered customer engagement
• Significant influence over architecture, engineering standards, and product direction
• High ownership and autonomy in decision-making
• A collaborative, global, remote-first engineering culture
• Continuous learning and professional growth opportunities
• Competitive compensation and benefits
• Flexible working arrangements built on trust and accountability

 

What they expect

They are looking for someone who can:

• Enjoy solving complex technical and product challenges while balancing speed and long-term maintainability
• Communicate effectively with both technical and non-technical stakeholders
• Work independently while collaborating in a distributed, remote-first environment
• Take meaningful ownership of system architecture and product direction
• Contribute proactively to engineering culture and technical standards

 

Career Opportunities

• Advance your expertise as an Engineering Lead toward roles such as Software Architect or Technical Lead
• Grow into Engineering Manager or CTO-track positions through involvement in both product and business strategy
• Play a key role within a global engineering organization

 

Required Skills & Qualifications

• 5+ years of professional software engineering experience
• Experience working in Agile and Scrum development environments
• Business-level proficiency in both Japanese and English
• Strong full-stack web application development experience
• Experience with frontend technologies such as React, Vue.js, or Next.js
• Experience with backend technologies such as Node.js, Python, Elixir, Ruby, or PHP
• Experience designing scalable APIs and backend systems
• Deep understanding of software architecture, system design, and technical trade-offs
• Experience with relational databases such as PostgreSQL or MySQL
• Experience owning production systems in live environments
• Experience mentoring engineers and leading technical initiatives
• Excellent communication, debugging, collaboration, and problem-solving skills
• Ability to thrive in ambiguous environments and proactively drive projects forward

 

Preferred Skills

• Experience with statically typed languages, including TypeScript or Python type hints
• Experience using gRPC and Protocol Buffers
• Experience with Elixir/Phoenix or functional programming
• Experience building scalable SaaS platforms
• Understanding of conversational AI and LLM-powered applications
• Experience designing event-driven architectures and distributed systems
• Experience collaborating closely with Infrastructure or DevOps teams
• Experience improving engineering processes and development workflows
• Experience working in fast-growing startups
• Interest in AI-assisted software development workflows

Ideal Candidate Profile

• Enjoys solving complex technical and product challenges
• Balances speed with long-term maintainability
• Communicates effectively with both technical and non-technical stakeholders
• Thrives in collaborative, distributed environments while working independently
• Takes strong ownership of systems and product direction
• Is passionate about shaping engineering culture and raising technical standards

 

Compensation & Benefits

Salary: JPY 7,000,000 〜JPY 11,000,000per year
Probation Period: 3 months

Location
The position is based in either Tokyo or Osaka, depending on the candidate’s preference. Fully remote arrangements can be discussed on a case-by-case basis.

The company offers a flexible hybrid work style, combining remote work with office attendance. Frequency of office visits varies, typically ranging from once a week to once a month.

Working Hours

• Standard hours: 9:00 AM – 6:00 PM (includes a 1-hour break; overtime may be required)
• Flexible working hours with core time from 10:00 AM – 4:00 PM
• For employees above a certain grade, a discretionary labor system applies according to company policy

Holidays & Leave

• Saturdays, Sundays, and public holidays
• New Year’s holidays
• Summer vacation
• Bereavement leave
• Paid leave (10 days granted upon joining, with additional days accrued based on length of service)
• Other holidays as specified by company regulations

Benefits & Perks

• Commuting allowance (bicycle commuting permitted)
• Company-provided laptop
• Company-provided mobile phone (for certain roles only)
• Flexible start time program (can be applied for every 2 months)
• Social insurance coverage (health insurance, employee pension, employment insurance, workers’ compensation)
• Life & health support leave
• Coverage of medical check-up expenses
• Childbirth and childcare support programs
• Club activities and social groups

Measures Against Secondhand Smoke: No Smoking Indoors

 

Hiring Process

• Number of interviews: Document Screening →Coding Test→1~4 interviews → Reference Check→Offer
• Application documents required: Resume / CV
• Interview language: Japanese/English

 

Please note: this position is open to candidates currently residing in Japan.