Retrofitting improves a ship beyond just limit breaks or stat enhancing. This upgrade system uses special blueprints acquired from missions, daily log in bonuses, events, exchange, or drops from hard mode maps.

Current list of ships available for Retrofit
Destroyer Destroyers Acasta, Amazon, Ardent, Ariake, Ayanami, Bailey, Cassin, Comet, Crescent, Cygnet, Downes, Forbin, Fortune, Foxhound, Hamakaze, Hatsushimo, Hammann, Hatsuharu, Javelin, Kagerou, Kamikaze, Kisaragi, Laffey, Le Mars, Mutsuki, Nicholas, Shigure, Shiranui, Sims, Tanikaze, Yuugure, Z1, Z23
Light Cruiser Light Cruiser Abukuma, Achilles, Ajax, Curacoa, Curlew, Émile Bertin, Helena, Isuzu, Jintsuu, Karlsruhe, Kinu, Köln, Leander, Leipzig, Mogami, San Diego, Yuubari
Heavy Cruiser Heavy Cruisers Exeter, Furutaka, Kako, London, Portland, Suffolk, York
Battleship Battleships Fusou, Hyuuga, Ise, Nevada, Oklahoma, Warspite, Yamashiro
Light Aircraft Carrier Light Carriers Bogue, Hermes, Langley, Long Island, Ranger, Shouhou
Aircraft Carrier Aircraft Carriers Hiryuu, Saratoga, Souryuu

When you first access the Retrofit screen of a ship, your options are very limited with access to a single upgrade, as seen below the first upgrade HP upgrade that increase this ships's maximum HP.

Modification1.png

Once you have unlocked the first upgrade, those connected to it can then be unlocked. There are a variety of upgrades that can increase: a ships stats, proficiency on equipment slots, and even unlock a new skill for the ship. If an upgrade has multiple connections then connect upgrades all must be learned before it unlocks.

Modification2.png

As you unlock further into the Retrofit tree, upgrades require additional blueprints. Upgrades will also have multiple levels, allowing access to the next upgrade only after unlocking the next attribute. Limit breaks are also required to progress further into each ship's Retrofit tree, a low level ship with no limit breaks cannot go very far into the Retrofit tree.

Once the Retrofit tree is fully completed, the ship gains a new skin and increases one level in rarity.

Community content is available under CC-BY-SA unless otherwise noted.