Terms of Service

1. You can use the Service as a guest without signing up. Guest records are tied to your device and browser. If you clear your browser data, you may not be able to keep your records.
2. When you sign up, please use a valid email address. Keep your password to yourself and do not share it with anyone.
3. Do not use your real name, someone else’s name, or hurtful words as your username. We may change usernames that are not appropriate.

1. The Classroom Plan is a service in which a teacher creates a class and students join it with a join code.
2. Teachers who create a class should explain to their students (and to parents or guardians, for children) how the Service is used and that records are visible to the teacher. Please ask students to use a nickname, not their real name.
3. Share the join code only with students in the class. If the code leaks, you can issue a new code from the class settings.
4. We may view the contents of a class to operate the Service, respond to inquiries, and check for misconduct.

1. The fees, payment methods, and payment timing for the Classroom Plan are as described in the Legal Notice.
2. Until March 31, 2027, all classes can be used free of charge as monitors. If you create your first class on or after April 1, 2027, it is free for 30 days from the day you create it. You will not be charged automatically when the free period ends.
3. The paid period is the period you paid for (one month or one year). It does not renew automatically.
4. We do not accept refunds or cancellations after payment, except where we were unable to provide the Service for reasons attributable to us.
5. When a trial or paid period ends, new students can no longer join and assignments can no longer be sent. Teachers can still view past records.

When using the Service, you must not:

1. Falsify times or records (having someone else solve for you, solving automatically with a program, tampering with network traffic, etc.)
2. Impersonate others or use someone else’s account
3. Enter names or content that hurt or harass other users
4. Interfere with the operation of the Service, such as by sending a large volume of requests or trying to break its systems
5. Violate laws or public order and morals

If we determine that any of the above applies, we may invalidate records or suspend use of the Service.

For problems submitted by users, we may use them free of charge within the Service (as problems, in contests, announcements, introductions, etc.), and may adjust their form or assign a difficulty. Please submit only problems you created yourself.

We may change the contents of the Service or temporarily suspend it for maintenance, outages, and similar reasons. If we end the Service, we will give notice as far in advance as possible. If any Classroom Plan has a paid period remaining, we will provide a refund or other remedy for the remaining period.

1. We do not guarantee that the Service will always run without interruption or that records will never be lost.
2. Even where we are liable to a user in connection with the Service, except in cases of our intent or gross negligence, our liability is limited to the amount the user paid us in the month in which the cause arose.

We handle user information as described in our Privacy Policy.

We may change these Terms when necessary. When we do, we will announce it within the Service. If you use the Service after a change, you agree to the revised Terms.

These Terms are governed by the laws of Japan. Any dispute relating to the Service shall be subject to the exclusive jurisdiction of the Tokyo District Court as the court of first instance.

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