She and her sister ship Ro-12 were the first submarines built to a fully Japanese design.

[1] Unlike European submarines, which could lie on the bottom in the shallow waters of the North Sea and the Mediterranean Sea, Japanese submarines needed superior depth control while operating in the deep waters of the Pacific.

[1] They also required stronger hulls than their European counterparts because of the tendency of the Pacific′s more powerful and unpredictable currents to disrupt a submerged submarine′s trim and force her below her intended operating depth.

[1] The Kaichu type thus were broader in beam in proportion to their length than European submarines of the period and had a greater amount of internal compartmentation and more bulkheads than was common in other submarines, resulting in more cramped and uncomfortable conditions for their crews but a hull strength that purportedly allowed them to survive collisions, groundings, and overly deep dives that would have destroyed European submarines.

[1] In 1921, at least some naval analysts claimed that the Kaichu type′s hull strength gave it a greater chance of surviving a depth-charge attack than any other existing submarine class.

For surface running, the submarines were powered by two 1,450-brake-horsepower (1,081 kW) Sulzer Mark II diesel engines, each driving one propeller shaft.

They were also armed with a single 76.2 mm (3.00 in) deck gun mounted aft of the conning tower.

19 was transferred to Submarine Division 3 and attached to the Yokosuka Naval District, in both of which she remained for the rest of her active career.