Matoi Shinonome attends Fujimisaki Academy, an institution gathering girls partnered with Z/X beings across Japan. Her partner Z/X is Sonne. Petite and openly affectionate, she frequently embraces Ena Soranokawa passionately in public, clinging to her arm and maintaining physical closeness in varied settings like the beach where she holds Ena’s body.

Matoi’s specialized Z/X card abilities include "Sun Moon Reunion" with the "Absolute Boundary" effect granting immunity to other card targeting. Its "Boot" ability requires trashing two "Sonne"-named cards from the charge area to summon a reboot-state "Sonne"-named Z/X from the trash, allowing up to three force cards beneath it. Another card, "Unite<S>," features flavor text where Matoi remarks on Sonne’s nature: "Destruction is... reason for... Sonne’s existence" and "Sonne... can still go on. That’s why... can go even more wild. Heheheh," emphasizing Sonne’s destructive potential and capacity for heightened intensity.

She appears in "Z/X Code reunion," depicting Fujimisaki students navigating Z/X partnerships after a tentative human-Z/X peace treaty.