In this case, you need to apply for acquiring status of residence for your baby. Please file the application at the regional immigration bureau that has the jurisdiction over your domicile within 30 days from the date of birth. When you intend to leave Japan within 60 days from the date of birth (excluding the case where you intend to depart from Japan on a re-entry permit (including a Special Re-entry Permit)), you need not file an application for a status of residence for your baby.
(source: Immigration Services Agency of Japan)
For inquiry to Visa and Beyond by Takatsuka Office, please send a message through a contact page.
Visa and Beyond Immigration Services 