To celebrate the launch of the Sakurasou Dengeki Website, early designs created by Keiji Mizoguchi for the main cast were shared alongside some comments about them. The descriptions have all been fully translated.
Another set of concept art released created by Keiji Mizoguchi released to the Sakurasou Dengeki website, this time featuring characters that were missed in the first batch alongside the two new characters introduced in volume 7. Once again, all comments have been fully translated.
Sakurasou Minutes, also known as Sakurasou Record of Proceedings, is a series of short text stories that were available on the original Sakurasou Dengeki website that released every Thursday from October 27, 2011 to March 28, 2013. It features chibi character portraits drawn by Keiji Mizoguchi, which would later be used on the Drama CD. Here you can find translations for all 74 Sakurasou Minutes stories alongside the three Sakurasou Minutes styled bookmarks for the Drama CD.
After finishing The Pet Girl of Sakurasou, Kamoshida and Mizoguchi would go on to create the Rascal Does Not Dream series which is set in the same universe. As a result there are a lot of references to and mentions of The Pet Girl of Sakurasou throughout the various light novels, manga, and anime, which are all documented here.