Ms. Koike’s best bet lies in focussing on women-friendly measures, such as increasing the choices for childcare and elderly care available. Although feminism as an ideology is surprisingly muted in Japan, women, in particular younger women, feel short-changed by a politics that is overwhelmingly male-dominated.

Based on existing laws, female members of the imperial family must give up their status should they marry a commoner. The same law does not apply to male members of the family and has long been a source of controversy for the Japanese imperial family.