He is President Funny Valentine's personal bodyguard. When Lucy Steel and Hot Pants infiltrate the President's residence in Chicago, he battles Hot Pants in order to protect Valentine. Mike O. is a Stand user and creates deadly metal balloons through his Tubular Bells.

Mike O. is a dark-skinned man of average to above-average height and medium build. His head is shaved save for a dark, curly patch on his crown; and centered on the edges of both eyes, extending to mid-forehead and covering his cheekbones, he has two light, swerving tattoos tapering at both ends into a spiral.

As a security officer, Mike O is highly dedicated to his job. When someone infiltrated a presidential building to intercept a message from Ringo Roadagain, Mike O. has led an exhaustive investigation on the staff and their relatives, making over 1000 detailed files. He takes his duty as a symbol of honor and has commented that finding Hot Pants in the presidential building was a breach that stained this honor. Mike O. was also very distressed when he discovered that the First Lady Scarlet Valentine had died under his watch. On the other hand, Mike O is extremely ruthless toward those that threaten the President. Wrathful about Scarlet Valentine's death, he then decided to kill both Hot Pants and Lucy Steel on the spot as an execution. Likewise, Mike O. requested that he could execute whoever stole Ringo's message.