If you want to move off SharePoint, migrate your documents from SharePoint to Box. This is useful for organizations moving content out of Document Libraries in SharePoint and into Box.
If your goal is to expose Box content in SharePoint and have a single point of access to content, then use Box Embed or Box shared links to expose Box content in a SharePoint portal. This is useful for organizations that have business processes or add-ons in SharePoint and want to use Box and SharePoint together without any customization.
If you want to have Box as a system of engagement and SharePoint as a system of record, you can use the Box API to publish and move data from one system to another, or you can work directly with Box partners that provide the SharePoint connector capability. This is useful for workflows such as publishing from SharePoint to Box, or for archiving content.