1. Application
These Terms of Use apply to the use of BookField, a reader app provided by Finite Field, and to related pages that describe BookField and the .wbpkg package format.
If app store terms, a distributor's terms, school or organization rules, or a separate written agreement apply to a user's receipt or use of a package, those terms may also apply. These terms do not replace rights that cannot be excluded under mandatory law.
2. Definitions
In these terms, the following words have the meanings below unless the context clearly requires otherwise.
- BookField or the App means the BookField reader app and related app components provided by Finite Field.
- .wbpkg or package means an installable content package that BookField can import, validate, and read on the device.
- Content means text, media, navigation data, study plan data, locator data, metadata, and other materials contained in or associated with a package.
- User means any person who installs, opens, imports, reads, searches, annotates, or otherwise uses BookField.
- Distributor means a person, school, organization, company, publisher, or other party that provides a package to a user.
- On-device data means imported package data, SQLite data, media files, annotations, highlights, bookmarks, reading progress, study plans, search records, settings, and related data stored on the user's device.
3. Conditions of use
A user may use BookField only after agreeing to these terms and any applicable app store terms. If the user is a minor, or uses BookField for a school, organization, or company, the user must obtain the consent or authority required by that context.
BookField may require a supported OS, device capability, storage capacity, app version, and package version. Some functions may not be available on every device or platform.
4. Feature scope
BookField focuses on reading installed packages. The app may support package import, Library, Reader, annotations, highlights, bookmarks, study plans, local search, structured reference resolution, and other related reading functions.
The current product baseline is the iOS implementation, with Android following the iOS behavior during parity hardening. BookField imports supported package data into local storage such as SQLite after import and does not parse EPUB, HTML, or CSS at runtime for the reader experience.
The initial BookField promise does not include cloud sync, account sync, server-side backup, or Reader-side authoring. Finite Field may add, change, or remove functions as described in these terms.
5. Packages and content
Users must import only packages that they have obtained lawfully and are permitted to use. Distributors are responsible for ensuring that packages and content they provide can be distributed and used lawfully.
Rights in package content remain with the relevant distributor, author, publisher, right holder, or user. Importing or reading a package in BookField does not transfer content rights to Finite Field.
Finite Field does not guarantee the content, accuracy, legality, safety, completeness, or educational suitability of third-party packages that Finite Field has not provided. Malformed, incompatible, unsupported, or unsafe packages may be rejected or may not work as expected.
6. On-device data and backup
BookField stores imported packages, SQLite data, media, annotations, highlights, bookmarks, reading progress, study plans, search data, and related records on the user's device unless a separate feature clearly states otherwise.
The initial service design does not provide cloud sync or server-side backup for BookField reader data. Users are responsible for device management and backup methods available through their OS, device, or organization.
On-device data may be lost if the app is deleted, the device fails, OS storage is cleared, the package is deleted, backup settings exclude app data, or an import or update fails. Users should keep original packages and any necessary backups by methods available to them.
7. Prohibited acts
Users must not use BookField in a way that harms Finite Field, other users, distributors, right holders, app stores, or third parties.
- Obtaining, importing, creating, distributing, or using packages that infringe rights or violate law.
- Unauthorized access, interference, excessive load, abuse of support channels, or attempts to bypass technical restrictions.
- Redistribution, analysis, modification, reverse engineering, or circumvention of BookField or packages except where permitted by law or by the relevant right holder.
- Using BookField or package specifications to mislead others, spread harmful content, or infringe another person's rights or interests.
8. Intellectual property
BookField, its app design, UI, logos, site text, specification explanations, software, and related materials are protected by intellectual property laws and other rules. Except for rights expressly granted, Finite Field and its licensors retain all rights in BookField.
Content inside a package does not become the property of Finite Field merely because the package is imported into BookField. Users retain any rights they have in their own annotations and other user-created on-device data, subject to applicable law and any package or organization rules.
9. Privacy
BookField is designed as a local-first reader. Reader data such as imported package data, annotations, reading progress, study plans, and local search records is stored on the device unless a feature clearly explains a different handling.
When a user contacts Finite Field through a website form or another support channel, the information sent through that channel is handled under Finite Field's privacy policy. If BookField later adds server-side sync or similar functions, the applicable data handling will be explained separately.
10. App stores and third-party services
Distribution through the App Store, Google Play, or another app store may be subject to the store's terms, review rules, payment rules, refund rules, and platform requirements. Those rules may apply in addition to these terms.
BookField may depend on OS and device functions such as Files, Open In, sharing sheets, storage, backups, accessibility settings, fonts, media playback, or network status. Finite Field is not responsible for every change or failure in those third-party functions.
11. Disclaimer of warranties
BookField is provided on the basis that users choose whether it fits their environment, packages, and reading needs. Finite Field does not warrant uninterrupted operation, permanent availability, complete compatibility, error-free import, complete search, complete reference resolution, or fitness for a particular purpose.
Package validation, Reader display, Search, Calendar, study plan display, reference resolution, and local storage behavior may be affected by package quality, device state, OS behavior, storage limits, app version, and other circumstances.
12. Scope of liability
Users are responsible for obtaining packages lawfully, preserving original package files, managing their devices, and keeping backups that are appropriate for their use. Finite Field is not responsible for packages or content provided by third parties except where mandatory law requires otherwise.
To the extent permitted by applicable law, Finite Field is not liable for lost data, lost profits, business interruption, indirect damages, special damages, consequential damages, or disputes related to third-party packages. Nothing in these terms excludes liability that cannot be excluded under mandatory law.
13. Changes, suspension, and end of provision
Finite Field may update BookField, change functions, change supported OS versions or package versions, suspend functions, or end provision of the app or related pages when necessary for maintenance, security, legal compliance, product improvement, store requirements, or business reasons.
When a change is likely to have a material effect on existing on-device data or package compatibility, Finite Field will make reasonable efforts to provide notice by an appropriate method.
14. Changes to these terms
Finite Field may change these terms when necessary because of legal changes, app changes, security needs, app store requirements, or operational needs. The updated terms will be published on this page or by another appropriate method.
Unless a different effective date is stated, changed terms take effect when published. If a change materially affects users, Finite Field will make reasonable efforts to give advance notice.
15. Notices and contact
Notices from Finite Field may be provided through this site, app store listing, in-app notice, email, or another reasonable method. User inquiries about BookField should be sent through the contact page linked from this page.
16. Governing law and jurisdiction
Unless mandatory law requires otherwise, these terms are governed by the laws of Japan. If a dispute must be handled in court, the court with jurisdiction over Finite Field's principal office will be the agreed court of first instance, unless mandatory law requires a different forum.
17. Severability
If any part of these terms is held invalid or unenforceable, the remaining parts continue to apply. The invalid or unenforceable part will be interpreted or replaced to the extent necessary to preserve the original purpose as far as permitted by law.
18. Anti-social forces
Users represent that they are not members of organized crime groups or other anti-social forces and will not use threats, violence, fraud, obstruction of business, or similar conduct in relation to BookField or Finite Field.
19. Language and translation
BookField is published on this site with Japanese as the default site language, and translations may be provided for users' convenience. If a release, app store listing, or in-app notice specifies a language priority, that specified priority applies to that release or notice.
20. End
These terms end the current BookField Terms of Use page.