kaga, akagi, zuikaku, ryuujou, houshou, and 10 more (kantai collection) drawn by ragho_no_erika

Japan's first aircraft carrier as well as the first finished ship designed from keel as an aircraft carrier. The design is based on data gained from actions of British aircraft carriers (and seaplane tenders) during World War 1. There’s also plan for second and third ship in her class. The second ship is planned to be named “Shoukaku”.

By the way, at that time there's still no specific class name like Aircraft Carrier. So when Houshou is launched in 1921, she's classified as “Special Operation Ship”

Houshou is then moved to Yokosuka Naval Arsenal to complete her fitting in December 1922. After that she went through many modification and tests. First is the take-off and landing trial/ Then the island structure is removed, modifying her to a flush deck design. Through those experiments and modification finally she became her operational form.

In 1924, her complementary are 6 Type-10 and 9 Type-13.

In history, there's no claim heavier than to be the "World’s first/most”. British and American already have aircraft carrier modified from warship. There’s also the class of aircraft carrier called Seaplane Tender where French Le Foudre holds title of world first. Japan also have Wakamiya as first seaplane tender.

1928: formed the 1st Carrier Division with Akagi.
1932: taking part with Kaga in the Shanghai Incident. Her airplane is the first Japanese ship to shoot down another airplane.
1934: formed the 1st Carrier Division with Ryuujou.
1935: her flight deck is damaged by storm (Fourth Fleet Incident) and received modification along with repairs.
1939: took part in the Battle of Shanghai and then moved as reserve ship for three years. In 1940 she's assigned to the 3rd Carrier Division.
1942, she's assigned to 1st Battleship Division in Battle of Midway carrying Type-96 and spotted the burning Souryuu.

After that, she’s assigned to training fleet operating in Seto Inland Sea. Nearing the end of the war, she's modified again to operate newer airplanes such as Tenzan and Suisei. In 1944 her flight deck is extended. This increased her size and made her unable to sail to the open sea. Her 14 cm cannon is also removed. In March 1945, she's damaged by Allied air raid on Kure. She received repair and saw the end of the war. As one of the few large sized ships left, Houshou is entrusted as repatriation ship and brought back more than 40 thousand people back to Japan. She's scrapped in 1946.