"I guess today's the day I'm getting a raise."
Yashiro is the first boss of The Quarter Game, disguised as the mystery man. He is a strong samurai who blends his techniques with ninja secrets, creating a brand new fighting style known as the Shirokawa style. He is the father of Mashiro, the protagonist of The Quarter Game. He fights her to test her skills if it is safe enough for her to save her mother. He loves donuts and always brings dozens home for his family.
He went missing for a while prior to The Quarter Game. To prepare for situations like these, he trained Mashiro in his fighting style so that she may protect her family and herself in times when he is in military missions.