- "Nothing goes without meaning."
- ―Mariko Yashida
Mariko was first seen crying over her dying grandfather; she briefly met Logan, calling him a caveman, and was also seen talking to her friend Yukio. She was then seen being hit by her father, Shingen Yashida. Ashamed, she attempted to commit suicide before Logan saved her.
At her grandfather's funeral, she was kidnapped by the ninja clan Yakuza, who were secretly hired by her fiancee, Noburo Muri, but was again saved by Wolverine. She then went to a house in the south, catching the bullet train with Wolverine following her. After Wolverine had a fight with the Yakuza, he took her off the train. She and Logan then headed to a local motel; as she slept, Logan stood outside guarding her. She later woke up to find him passed out. She then got the motel owner's grandson, who is a veterinarian, to stitch him up.
Logan and Mariko then hid in Yashida's house down south, and as they started to fall for each other, Logan revealed moments from his past such as the war and Jean.
Mariko was then kidnapped and taken to her father Shingen at the Yashida family home, where it was revealed that her grandfather had left her the empire and her father prepared to kill her. Kenuichio came to save her with a Black Ninja clan and took Mariko to a research center base where Yashida was born.
After Wolverine came to save her, she talked to Harada and escapes. She managed to direct the machine Logan was in into the Silver Samurai's sword strike, breaking it and freeing him. Mariko then killed Yashida with Wolverine's claws. After that, he started to extract his immortality and ultimately fell to his death because of Wolverine.
Mariko became the CEO of Yashida Corporation and said goodbye to Wolverine, hoping to see him again.
- In the comics, Mariko and Harada are half siblings.
- In the comics, her fiancé Noburo Mori is Noburu Hideki her husband.