Sakura Wars: Kinematron Hanagumi Mail

Sakura Taisen Kinematron Hanagumi Mail (サクラ大戦キネマトロン 花組メール) is a piece of Sega Dreamcast software distributed exclusively with Sakura Taisen-branded Dreamcasts.

It is essentially a glorified emailing service, in which the user can send emails with Sakura Taisen imagery. In order for the recipient to see the added features, he/she must also own this disc, otherwise the email will be rendered simply as text (which effectively means the recipient must own a Sakura Taisen Dreamcast). Given the state of the Dreamcast's online capabilities in the modern age, the disc is largely unusable today.