So, games just released, it's not that bad to play and it's doing good.

Now, you want to S-Rank Mission? You should do it on NORMAL difficulty.

How do you this this quick and Easy?

Well, it's easy for the most part, quick? Not so much.

The best method I found is to find the invisible wall and walk around it while ignoring objectives.
(The blinking yellow circles on the minimap)

Next up, use your Eyes, look around everywhere while sticking to the wall, maps will probably be map later by some dedicated community members but right now you have to relay on yourself. So keep em wide and pay attention to the minimap.

Now, "How do I get S-Rank?"

So far it seems every boss gives 30k score, so what you want to do is go around killing every mob you can until you reach roughly 20k score. Then you kill the boss and you get S-Rank.

Mobs spawn On, Off and around the beaten paths, do not be afraid to run around in the middle of nowhere, you might find a couple mobs to kill.

If you get around 16k and can't find any enemies just go do the yellow circles, you'll most likely have multiple of them in a row that will get you to 20k before the boss.

Consoles and "Named" enemies will give you little quests that give you bonus score which will make things go by faster.

Remember, just go around the entire map, keep your eyes out for extra Named boss monsters, remnants and consoles and chests. Collect everything you can.

Now, final thing to present to you.