The titles of honor of crown prince and crown princess are Imperial Highness like other Imperial Princes and their empresses and Imperial Princesses and princesses (Clause 2 of Article 23 of the current Imperial House Law).
皇太子と皇太子妃の敬称は、他の親王・王とその妃、および内親王・女王と同様に殿下である（現行皇室典範23条2項）。