Cardfight!! Vanguard Shinemon Arc

Years before Aichi and friends came into play Misaki's parents were killed in a car accident. A young Shinemon Nitta vows to protect Card Capital so that Misaki can inherit it. However a family friend, Esuka, now owns the deed. If that weren't enough a local scientist is also out to prove that Cray exists. The story of Shin's past as Shinemon and how he becomes the manager of Card Capital is finally revealed.

Synopsis from Anime News Network