The Lost Brother (Male reader x Girls und Panzer)

(Y/N) Nishizumi got 6 years old when is first sister Maho come into his life when she come to life his mother forgot him and more when his sister Miho arrive even if he hate his mother, he love his sister even if they don't know they have a brother, he leave in Germany with the help of his father, (Y/N) is a fan of Tank, he was a great tactician, one day when he was 15 years old, he found the construction diagrams of the E 75, everyone said he could never build that Tank but only 1 years later, he finally build it. He accumulate money, with this money he create a Factory to create tanks that never be build, now aged of 21 years old, he came back to see the finale of Sensha-Do between Oorai and Kuromorimine but he is famous not for his family name but for his nickname the master tactician of Panzer