Mika Kisaragi serves as a mentor and protective older sister figure, recognized by her brown hair, purple eyes, and signature outfit: a white t-shirt with blue sleeves, blue shorts, and a pink apron. Her kindness shifts to sternness around Arata, their interactions laced with sharp banter and unspoken tension, while she gently supports Hajime and other younger characters.

Employed at a Battle Spirits shop, she once led her school’s club under advisor Keisuke Saimon before retiring from active competition after her pivotal card, The ArcAngelia Mikafar, was banned. Despite abstaining from battles, she covertly trains Hajime following his Hero Championship defeat, disguising herself as the enigmatic Battle Spirits Sage to challenge him in costumed duels at a dojo. Her identity is revealed to Hajime prior to the world tournament, though others had already pieced together the truth.

Her deck specializes in Pentan-type spirits and nexuses, featuring The SuperEmperor Siegpentan-Nova, The Butler Pentan, and The Empire of Pentan: the Capital Empereur. Blending yellow and white attributes, it employs spirits, braves, and strategic magic cards such as Wing Boots and Reboot Code.

Mika navigates relationships as both mediator and motivator, fostering a sibling-like bond with Hajime that pushes his growth. Her dynamic with Arata balances rivalry with mutual respect, punctuated by teasing and subtle romantic undertones from his side.

Linked to a namesake character from another manga through The ArcAngelia Mikafar, her story intertwines her past as a formidable battler with her current guidance role, emphasizing mentorship as her path to personal growth.