Hi,
You could have guest checkout and the access to the video could be made based on the purchase status of a product with the 7 videos added to it in its "files" area.
Another solution would be to use the hkshow content tags of HikaShop around the area where the videos are accessible (like a Joomla article for example):
www.hikashop.com/home/blog/466-hikashop-4-4-1.html#tags
This would also work with guest checkout.
But if you don't want to use the "files" area to give access to the videos and you can't use the content tags (if the videos are made available to the user via another extension which doesn't support content tags for example), then, instead of linking the product to the video files directly, you would have to link the product to a Joomla user group thanks to the "user group after purchase" setting of the product, and then you could configure the area where the 7 videos are accessible to be restricted based on the user group of the user. And in that case, it would require registration.