[2] The HTV is comparable in function to the Russian Progress, the ESA ATV, the SpaceX Cargo Dragons, and the Cygnus spacecraft, all of which bring supplies to the ISS.

Unlike Progress spacecraft, Cargo Dragon 2's and ATV's which use the docking ports automatically, HTVs and American Dragon 1 approach the ISS in stages, and once they reach their closest parking orbit to the ISS, crew grapple them using the robotic arm Canadarm2 and berth them to an open berthing port on the Harmony module.

With the extension of the ISS project through 2028, three more missions were added, with the tenth flight seeing an improved, cost-reduced version called the HTV-X.

In May 2015, Japan's Ministry of Education, Culture, Sports, Science and Technology announced a proposal to replace the HTV with an improved, cost-reduced version preliminary called HTV-X.

[11][26] In December 2015, the plan to develop HTV-X was approved by the Strategic Headquarters for Space Policy of the Cabinet Office, targeting launch in fiscal year 2021 for the flight of HTV-X1 (Technical Demonstration Vehicle) by the H3 rocket.

[28] As of 2021[update], an evolutionary version of HTV-X called HTV-XG is being considered for transferring cargo to the Lunar Gateway as part of the Artemis program.

[32][33] Further, conceptual plans in 2012 included a follow-on spacecraft design by 2022 which would accommodate a crew of three and carry up to 400 kilograms (880 lb) of cargo.

[34] As of 2014[update], both JAXA and Mitsubishi conducted studies of a next generation HTV as a possible Japanese contribution to the proposed international crewed outpost at Earth-Moon L2.

[35] A proposal announced in June 2008, "Preliminary Study for Manned Spacecraft with Escape System and H-IIB Rocket" suggested combining HTV's propulsion module with a human-rated capsule for four people.