Some tiaras/parures are either wedding gifts and guarantee a lifelong "possession", and some of them were made specifically for the princesses on their 20th birthday - but when a princess marries a non-royal or passes away, all the bling goes into the possession of the Imperial Household Agency (IHA).
So there are some actual ones
Princess TakamadoHer wedding tiara, a second diamond bandeau tiara, and the Mikasa Pearl Drop Tiara from her mother-in-law, who doesn’t attend tiara events anymore.
Princess Noriko of TakamadoPearl & Diamond Wave Tiara
(made by Mikimoto in 2008)
Princess Ayako of TakamadoDiamond Wreath Tiara
(made by Mikimoto)
Hanako, Princess HitachiJapanese Pearl Fringe tiara
Princess Tomohito of MikasaPearl & Diamond Tiara
Princess Yōko of Mikasa Pearl & Diamond Tiara

Princess Yuriko of MikassaDiamond Kokoshnik Tiara
One is to be know been taken apart and remade

Empress Shōken Scroll Tiara
(which the Meiji Scroll Tiara was made of)
And others nobody knows what really happened to them
Princess Takamatsu’s Floral Palmette Tiara - we haven't seen that one yet
Crown Princess Bangja Tiara- no one knows where that is
Princess Chichibu Pearl Drop Tiara(made by Mikimoto circa 1936)
- no one knows where that is

Princess Itsuko of Nashimoto (1882 - 1976)* Married Prince Nashimoto Morimasa
* Mother of Yi Bangja, Crown Princess of Korea (born Masako)
* Aunt of Princess Chichibu (Setsuko)
- 2 tiaras nobody has seen
Empress Kojun Scroll Tiara(made by Mikimoto)
- not seen in ages