|“||This won't end here... Your battle will never end.||„|
|~ Masako Suzuka's last words.|
Masako Suzuka is the assistant of Hideyasu Jonouchi who secretly plans to spread Helheim fruits all throughout the world and the main antagonist of the Kamen Rider Gaim two-part special Gaim Gaiden: Kamen Rider Gridon VS Kamen Rider Bravo.
She was portrayed by Tomomi Jiema Sumi.
At an unknown point in time, Masako became the assistant of Hideyasu Jonouchi, who had risen to become a world famous pastry chef after taking over Charmant from Oren Pierre Alfonzo. Secretly, Masako broke in and stole some mutated Helheim fruits Takatora Kureshima was using for research purposes, planning to use Jonouchi's cover as a pastry chef to distribute them all throughout the world and cause chaos. Seeking to unmask the culprit, Takatora hired Oren to go after Jonouchi in order to get the true culprit to reveal himself.
Oren later issued a challenge to Jonouchi to come meet him, which Masako brought to Jonouchi's attention. Jonouchi agreed to the challenge, and Masako drove him to the meeting spot. When Oren showed up to confront Jonouchi and transformed into Kamen Rider Bravo, a pair of Helheim vines suddenly appeared and wrapped around Oren, converting him into the mindless Bravo Kingdurian Arms. As Jonouchi transformed into Gridon once more to stop the rampaging Bravo, Masako watched from afar. Takatora then approached her and identified her as the real mastermind behind the stolen Helheim fruits. Her cover blown, Masako pulled out a Sengoku Driver and the Hells Lockseed, which she used to transform into Kamen Rider Sylphi.
While Gridon Lychee Arms fought Bravo Kingdurian Arms, Takatora transformed into Zangetsu Kachidoki Arms and fought Sylphi. He finally defeated her by striking her with his two flags. Right before dying, Sylphi faded away told Takatora that it wasn't over and his battle would never end. Takatora said that he already knew, and that that was how it was meant to be.
- Masako's actress, Tomomi Jiena Sumi, is a member of the Kamen Rider Girls and represented Kamen Rider Gaim until 2016. She is the first and thus far only Kamen Rider Girls member to portray as an actual Kamen Rider.