Alright. One of the Super Nurds have relayed information regarding the upgrade cues we receive for the Servant. He stated that the cue known as "Upgrade_ready_0" has never been heard and if it has, it was by mistake. I'm here to say that, after reviewing what the quote is and what it sounds like, I have heard it in a legitimate playthrough. However, I heard it while wielding a sword. Now, I haven't been involved, recently, in discovering new cues and such as I have a life that needs to be lived. Yet, I still have a strong interest in this world of imagination so I'm sticking by until my mind cannot last in this biome.
So, this audio cue is related to the servant but only occurs with a sword. It's as if, in order to upgrade the servant, we need to have completed most of everything else. At least when considering the swords in their normal state. The process to upgrade the swords is another quest all their own. The one thing that puts it all together is the audio cues we receive. The question that remains is: "Do we need to reach a point in our journey before attempting an upgrade?" I ask this because if according to Super Nurd, Downtown Fuck, we need these cues to progress than this means we need certain quests to be completed prior to engaging a further quest. Well'p I'm going to head back to hentai and thinking about 'Making a Murderer'. Good luck with this stuff.