Jillian Chen is a supporting character in the Cardfight!! Vanguard anime, specifically appearing in the Asia Circuit arc. She is a descendant of the Soryu people, the same lineage as her leader, Leon Soryu, whom she and her sister serve. Jillian is the older twin sister of Sharlene Chen, and the two are members of Team Dreadnought.

In terms of personality, Jillian is portrayed as the more serious and passionate of the two sisters. She has a spirited and confident nature, often acting as the straight woman to her younger twin's more carefree and outspoken behavior. She can come across as having a pretentious demeanor, appearing to look down on others, but she is also shown to be more skeptical than her sister regarding the legend of the Soryu child, a key element of her team's background, which can sometimes lead her to jump to conclusions.

Jillian's role in the story is primarily as a member of Team Dreadnought during the VF Circuit. The team represents the Hong Kong stage of the competition. In the tournament, Jillian and her sister Sharlene fought together as a tag team, successfully advancing to the semifinals. For the final match, she took a supporting role on the sidelines as Leon stepped in to fight. Beyond competitive cardfights, Jillian is also physically capable. In one instance, she and her sister easily defeated two members of Team Avengers without the use of weapons, implying she has knowledge or training in martial arts.

The key relationships in her life center on her twin sister, Sharlene, and her leader, Leon Soryu. As Sharlene's older sister, she frequently provides commentary and reactions to her sibling's wilder impulses. Her loyalty to Leon is a defining characteristic, as she and her sister are dedicated to serving him. Her other notable encounters include a cardfight against Osamu Kishida, which she won, and a subsequent fight against Fajil Ali, whom she lost to.

Jillian's development and abilities as a cardfighter are difficult to assess in detail. Although she participates in several cardfights throughout the Asia Circuit and subsequent Link Joker arc, the actual content of her battles is almost always omitted or off-screen, making her specific strategies and skills largely unknown. Her recorded fights include a tag battle alongside Sharlene that went unfinished and the two individual battles against Kishida and Ali. She makes a later reappearance in the series Cardfight!! Vanguard G: Gears Crisis Arc, though she does not participate in any direct fights during that time.