Being forever known as 'that time Japan tried to loophole a treaty' is probably a distinction for Ryujo. A light carrier, that was intended to take advantage of poor wording in the Washington Naval Treaty.

Namely that any ship under 10,000 tons- no matter the actual design -didn't qualify as an aircraft carrier. Or, at least, didn't count towards the treaty mandated displacement limitation.

Thus, Ryujo. A ship that suffered stability issues and other problems due to compromises in her design and construction. Yet, a ship that actually proved quite successful in actual service. An interesting set of contradictions, really.

Further Reading:
https://www.amazon.com/Imperial-Japan...
https://www.amazon.com/Warships-Imper...
https://www.amazon.com/Imperial-Japan...
http://www.combinedfleet.com/ryujo.htm