When a player applies a buff to themselves/teammate or a debuff to an opponent a medal will appear on the top left screen, if two players are quickly pressing Triangle to encourage this will fill up the medal bar quickly also including your weapon ult!

In co-op however you will lose the weapon ult if you get down.

Also I think that within PvP weapon ult duration are reduced much shorter than in story mode/co-op

Takes 30 seconds if you ignore all enemies and just run to the area. Its the only map that's the quickest however not ideal for getting shards and chunks. I also put in some tips when facing him!

More Arima guides:

Defeat CCG Reaper easily

[b][url=https://www.animeesports.com/Thread-How-to-easily-get-Kishou-Arima-Quinque-Shards-UPDATED--911]Kishou Arima -Quinque Sha