What if Saitama has a biological sister?

Nancy v.s Boros

*In the throne room*

Both exchange punches and Nancy enjoyed trading blows.

Boros launches barrage of punches towards Nancy but Nancy deflected all of Boros' attacks using her martial arts.

Both moving at almost light speed.

Boros: "Great! I can't believe someone can keep up with me! Let's do this in a serious way!"

Boros increased his movements speed and attack speed, lunging consecutive punches towards Nancy.

Nancy was shocked to how fast Boros' attack is.

Nancy: "I can't believe it...."

Boros: "haha! Was it too fast? Giving up now?"

Nancy: "I can't believe someone can put up a fight on me!"

Boros: "NANI!?"

Boros gets mad as he launched a roundhouse kick towards Nancy but Nancy evaded and grabs the foot of Boros before she slam him down to the floor, huge quake after the impact destroying the entire area and cracking the floor

Boros only receive slight damage.

Boros: "this is getting interesting, but I can't believe you are still bold despite fighting me in your dire situation"

Nancy: "Stop talking to me, give me your best shot"

Boros: "then how about this!?"

Boros suddenly sprinted so fast he was blinking infront of Nancy, he gives Nancy a powerful punch to the gut destroying the sound barrier and sending Nancy crashing to 7 thick walls as rubble falls from the impact.

Nancy's mouth and nose bleeds.

Boros smirks as he dashes forward, follow upping an attack with a jump kick.

Nancy gets angry as she sweep away Boros' attack before she counterattack with a powerful punch to the face enough to crack the skull of Boros. The impact was so strong it creates a shockwave turning all debris into powder, Boros goes pushed back and got slammed to the 7 thick walls with a fatal injury on his head.

Boros: *coughs blood* "impressive, such a powerful attack enough to kill a being like me but that won't matter if I have regeneration"

Boros grins widely as he regenerated his injury back to normal state.

Nancy can't believe it, she knows she will lose in a battle of attrition.

Nancy: "damnit, this is gotta be pain in the ass"

Boros: "now let's see how long can you lasts, can you even survive longer than my previous opponents?"

Boros moves so fast he dashes at zigzag movement, before he leaps towards Nancy and launching barrage of punches, each punch produce a shockwave that can shatter buildings.

Nancy grit her teeth as she raised her arms to defend in x shape, blocking all attacks but she seem in pain considering the amount of power from Boros is immensely overwhelming to her.