'Quickage' is a general term used for precise movement at the beginning of Hikage, with the purpose of spraying some graffiti before the cop dialogue ends and the cop fights trigger.
Initially, the term 'Quickage' was only used to refer to a specific jump in western Hikage; nowadays, Hikage has been rerouted and we now do the northern section first, so 'Quickage' has evolved to a more context-oriented definition.
Old Quickage is what was used on the English versions of Hikage back in ~2016 to reach the top graffiti before the English dialogue ended. You must jump at the top of the incline, and flick away from the staircase in the air so you pass alongside the upper stairs and cling to the rail there. This technique works in all similar staircase setups in JSRF, but technically speaking, only this precise location and scenario can be called a Quickage.
Japanese QuickageDiscovered by olo_ili, June 2017
Because Japanese cop dialogue is much faster than English, the Old Quickage was no longer enough to reach the graffiti in time. Due to this, a former IL strat was made viable and has since been dubbed 'Japanese Quickage'. The new viability of this strat was a big part in making Japanese the current fastest version.
This jump is 2-3 frames perfect and requires an identical speed + camera setup every time for it to be consistent. Basically, you are jumping at the exact corner of the rail so that you land onto the upper rail above you. What makes this jump work is that you are getting the additional vertical velocity that you get from an inclined rail, plus the new direction from rounding the corner of the rail. There is a very small window of time where these two requirements intersect, which is why this jump is so precise.
I personally use the electrowolf setup (tutorial is in the video to the right): Jump onto the higher rail, then ride it out almost till the end. Then hold right and jump over to the next rail - keep right held until the end of the trick. Once you land on the next rail, do 1 X trick and then wait for the corner (remember you still have right held). Jump right as you hit the corner, and you should do a very high hard right jump, and land on the upper rail (you can return the stick to neutral now). From there, you can start spraying the graffiti, starting with the S in front of you. Note: This method being called 'electrowolf setup' is misleading as electrowolf never actually followed this method completely, although some parts were similar.
This jump is considered one of the toughest in the game, especially when the Hikage route used to do the western area first, meaning you only had 1 or 2 tries at this jump before the cop fight started. Now, since we do the northern section first, Japanese Quickage is no longer required. However it's still the fastest way of reaching the western graffiti, so this jump is still optimal.
Quickage 2.0Discovered by Electrowolf, May 2019
The optimal route for Hikage nowadays is to do the northern section first - as is tradition, the level begins with very tight movement to spray some graffiti before the Terror Drone spawns.
Left Side Cop Skip
By performing Japanese Quickage on English, you can actually finish all the graffiti and leave the western area before the cop dialogue finishes, skipping the entire cop fight. This is currently the optimal way of clearing this area on the English version.
Cop Fight Disable (Featherpress)Discovered by FeatherData, July 2019
By unlocking a soul or collecting a mystery tape at a precise moment during a cop dialogue, you can freeze the cop dialogue so it never finishes. Similarly to Dark Side Cop Skip in 99th Street, since the cop dialogue never has a chance to finish, the cop triggers never spawn and you skip any remaining cop fights (which in this case is all of them). This trick is frame perfect and there is no current setup, so it is not currently RTA viable. This trick is also only confirmed possible on the English version as the cop dialogue for other languages is different.
Suprix BlessingDiscovered by suprix, ~2017
This is a small piece of movement at the end of the eastern part of Hikage, where after you spray the M, you do a small quickturn + hop during the graffiti camera, and fall optimally onto the lowest rail. Legend has it that if you perform it correctly, suprix has blessed your run.
Special ChallengeResearched by ycarcomed, April 2019
Hikage's special challenge is not particularly well-explained in the GG notebook and can cause some confusion. There are 2 checks done by the game to unlock this challenge: A 2-second grind on the top floor, then a landing. Players must ascend, with or without use of the crane (or even just skate up), grind for more than 2 continuous seconds on any of the top rails, then land in a decent sized area around the base of the stairs.