Soon after Iron Man (Tony Stark) battled Firebrand on the island of Isla Suerte, she started dating Stark largely as an act of rebellion against her parents who disapproved of Stark.
Rumiko's romance with Stark enjoyed many highs and lows. She enjoyed his jet-set lifestyle but found him often too obsessed with his work and failing to pay enough attention to her. This fact was made even worse due to all the problems facing Stark in his other life as Iron Man at this point, such as his armour temporarily becoming sentient and attempting to kill him, or the arrival of the Sons of Yinsen, a group dedicated to the memory of the scientist who helped Stark develop the original Iron Man armor.
At one point she engaged in an infidelity with Stark's business rival and enemy, Tiberius Stone. When Stark caught them together, the relationship ended. In remorse, Rumiko arranged for Stark to acquire sufficient stock in his old company for him to reclaim control of it.
Rumiko was later murdered when she was attacked by an Iron Man impostor named Clarence Ward.