Terms of Service

Article 1 (Scope)

1. These Terms apply to all relationships between users and the Operator concerning the use of the Service.
2. Guidelines and notices published by the Operator on the Service form part of these Terms.
3. If a separate agreement exists between the Operator and an organization (such as a company or educational institution) for an organizational plan, that agreement prevails over these Terms.

Article 2 (Definitions)

In these Terms, the following definitions apply.

• "User": any person who uses the Service after agreeing to these Terms
• "User Content": source code, profile information, and any other information a user submits or registers on the Service
• "Service Content": problems, test cases, explanations, learning materials, and any other information the Operator provides on the Service

Article 3 (Account Registration)

1. Some features of the Service require an account. Applicants must register with true and accurate information.
2. The Operator may refuse registration if false information is provided, if the applicant has previously violated these Terms, or if the Operator otherwise deems the registration inappropriate.
3. Users must promptly update their registered information whenever it changes.

Article 4 (Account Management)

1. Users are responsible for managing their credentials, such as passwords, and must not lend or share them with third parties.
2. Any action performed using a user's credentials is deemed an action of that user.
3. Users must promptly notify the Operator if they suspect unauthorized use of their account.

Article 5 (Use by Minors)

Minors must use the Service with the consent of a parent or other legal guardian. When a minor uses the Service, such consent is deemed to have been obtained.

Article 6 (Fees)

1. Basic features for individuals are currently provided free of charge.
2. Fees and payment terms for paid plans and plans for organizations or educational institutions are as presented at the time of application or as set out in a separate agreement.
3. If the Operator introduces charges for features currently provided free of charge, or changes any fees, it will announce this on the Service in advance.

Article 7 (Intellectual Property)

1. All intellectual property rights in the Service and the Service Content belong to the Operator or their rightful owners. The license to use the Service under these Terms does not transfer any of these rights.
2. Users may use the Service Content only to the extent necessary to use the Service, and must not copy, republish, redistribute, or sell problems, test cases, or other materials without the Operator's permission.

Article 8 (User Content)

1. Copyright in User Content, such as submitted source code, remains with the user.
2. Users grant the Operator a royalty-free license to use User Content (including copying, executing, analyzing, and displaying it) for grading and evaluation, displaying results, investigating defects, and improving the quality of the Service.
3. As part of the Service's design, the source code of accepted (AC) submissions is made public to other users. By submitting, users consent to this.
4. Features such as rankings and public profiles display usernames, results, and similar information to other users.
5. The Operator may remove User Content that violates laws or these Terms without prior notice.

Article 9 (Prohibited Conduct)

Users must not engage in any of the following when using the Service.

• Conduct that violates laws or public order and morals, or that is connected to criminal activity
• Conduct that infringes the intellectual property, privacy, or other rights or interests of the Operator or third parties
• Unauthorized access, probing or exploiting vulnerabilities, or attempting to escape the code execution environment (sandbox)
• Circumventing or deceiving the grading system, such as by improperly extracting test cases or falsifying results
• Impersonating others, or transferring, lending, or sharing an account
• Mass access or scraping by automated means, or any other conduct that places an excessive load on the Service
• Conduct that interferes with the operation of the Service
• Improperly collecting information about other users
• Providing benefits to or otherwise cooperating with antisocial forces
• Any other conduct the Operator reasonably deems inappropriate

Article 10 (Suspension and Termination of Accounts)

1. If a user violates or is likely to violate these Terms, the Operator may, without prior notice, remove User Content, restrict use of the Service, or suspend or delete the user's account.
2. The Operator is not liable for any damage arising from such measures, except in cases of willful misconduct or gross negligence by the Operator.

Article 11 (Withdrawal)

Users may withdraw from the Service at any time through the procedure specified by the Operator. Withdrawal requests are accepted through the Service's contact form.

Article 12 (Changes, Interruption, and Termination of the Service)

1. The Operator may change or add to the Service at any time, and will endeavor to give advance notice of significant changes.
2. The Operator may temporarily suspend the Service for maintenance, system failure, natural disaster, or other unavoidable reasons.
3. If the Operator terminates the Service, it will in principle give advance notice within a reasonable period.

Article 13 (Disclaimer of Warranties and Limitation of Liability)

1. The Operator does not warrant that the Service is free of de facto or legal defects, including defects relating to safety, accuracy, completeness, usefulness, or fitness for a particular purpose.
2. The Operator is not liable for any damage users incur through use of the Service, except in cases of willful misconduct or gross negligence by the Operator.
3. Even where the Operator is liable, its liability is limited to direct damages that would ordinarily arise, and is capped at the total fees the Operator received from the user in the preceding 12 months for paid-plan users, or 5,000 JPY for users on the free plan. This cap does not apply in cases of willful misconduct or gross negligence by the Operator.
4. Nothing in this Article limits the application of the Consumer Contract Act of Japan or other mandatory laws, and this Article does not apply to the extent it would be invalid under such laws.
5. Users must resolve any dispute with a third party concerning the Service at their own responsibility and expense.

Article 14 (Exclusion of Antisocial Forces)

Users represent and warrant that they are not members of organized crime groups or other antisocial forces, and that they have no relationship with such parties.

Article 15 (Amendments to These Terms)

1. The Operator may amend these Terms pursuant to Article 548-4 of the Civil Code of Japan when the amendment is in the general interest of users, or when it does not conflict with the purpose of the contract and is reasonable in light of its necessity and appropriateness.
2. When amending these Terms, the Operator will set an effective date and announce the amended terms and the effective date in advance by posting on the Service or by other appropriate means.

Article 16 (Communications and Notices)

1. Notices from the Operator to users are given by posting on the Service or by sending to the registered email address, and are deemed received at the time they would ordinarily arrive.
2. Communications from users to the Operator must be made through the Service's contact form.

Article 17 (Assignment of Rights and Obligations)

1. Users may not assign or pledge their position or any rights or obligations under these Terms to third parties without the Operator's prior written consent.
2. If the Operator transfers the business relating to the Service to a third party, the Operator may transfer its position under these Terms, its rights and obligations, and registered and other user information to the transferee, and users consent to this in advance.

Article 18 (Severability)

If any provision of these Terms is held invalid or unenforceable under applicable law, the remaining provisions remain in full force and effect.

Article 19 (Governing Law and Jurisdiction)

These Terms are governed by and construed in accordance with the laws of Japan. The Tokyo District Court has exclusive jurisdiction as the court of first instance over any dispute concerning the Service.