Obaasan is Japanese for 'grandmother'.
Grandmother to Ren, Riko and Hiro, Obaasan has brought the little ones to the WATI Museum for the evening when Zoë Castillo is there. She appears to genuinely enjoy the exhibits, though in Zoë's opinion they're little more than WATI adverts. She is also trying to keep Hiro from playing with the BunnyBot exhibit and not always succeeding, much to the museum guard's irritation. She ends up trying to deactivate the BunnyBot with the others when Hiro turns it on.
Obaasan is voiced by Deirdre Donnelly.