Mercy Walker

Megumi Aso (麻生 恵) is the leading female protagonist on the 2008 side of Kamen Rider Kiva. She is one of the users for the IXA System and in the SIC Hero Saga, she becomes Kamen Rider Kiva-la.

Personality
As a Fangire Hunter, Megumi makes it her personal duty to finish her mother, Yuri Aso's unfinished affairs, such as the Rook. She meets Wataru and develops a liking towards him after helping him with his allergy issue, unaware that he is actually Kiva himself. She is also not afraid to tell him off whenever he acts strange. While Keisuke Nago has expressed his interest in her, Megumi cannot stand him and was reluctant to notify him of Kiva's reappearance. However her feelings for him change throughout the series, eventually marrying him. She seems to share her mother's cynophobia.

Over time, she starts to see Kiva in a different light as he continues to fight the Fangire, rescuing her on more than one occasion in the process. When Mamoru Shima orders the elimination of Kiva, together with Nago she tries to assassinate Kiva but cannot do it.

Fangire Slayer
Megumi's main weapon is a rather small pistol that shoots slugs at high velocities, with an attachment which shoots out a chain that resembles her mother's Fangire Slayer.

Ixa
Megumi is one of the four 2008 users of the IXA Systems. She along with Ryo Itoya are the only users to not use the Rising Ixa function.

Kiva-la
In the S.I.C Hero Saga side story King of Vampire (which is an alternate ending to Kamen Rider Kiva), at the end of the wedding Kiva-la shows up instead of Masao Kurenai to warn everyone about the threat of the Rook's Sabbat. Kiva-la chooses Megumi to become Kamen Rider Kiva-la.

History
Megumi has occasionally been seen on the sidelines offering some help to the series Kamen Riders, sometimes becoming Kamen Rider Ixa, specifically to combat the Rook and other major threats when Nago is unable to. She is able to convince her younger brother to let her stay with the Fangire Hunters after she defeats the Rook. After Wataru goes into self isolation, after his outburst due to his awakened Fangire Blood she and Nago try to cheer him up to no avail. Megumi helps Nago to continue to fight as Ixa when his eyesight is failing and he is considering quitting. After the final battle, she marries Nago and tries to help with the new threat of the Neo-Fangire, but the guests keep her from doing so to keep her from ruining her dress. However, in the SIC Hero Saga, Kivala appears and grants Megumi the ability to become Kamen Rider Kivala in order to fight against the Rook's Sabbat with the other riders.