Dusk Diver 2

Story-related and cannot be missed.

This trophy is for completing Chapter 9, "Salvage, Sally". At the very beginning of the Chapter, you're informed that all side quests have been put on hold. While you can run around, visit different areas, etc., there isn't much to do at this point, as they want you to just head straight to the main quest after you make any "preparations" (e.g. buying items, upgrading skills, etc.) that you need to do.

It's a rather brief quest though, so it shouldn't take you very long. You'll have to go through Dadaocheng (Youshanding) to get to your main goal, the Tamsui River. This is a rather unique location, once again with its own, unique mechanic.

To allow you to cross the river, Boss manages to use a special machine to freeze parts of the river. However, there are still some bits of ice that are too far apart to cross, so to fix that, you'll need to use explosives to blow apart bits of the ice. You'll notice that throughout the whole area, there are the remains of many dead and destroyed robots. You can collect intact robot cores from their remains to explode the leftover robots (marked on your map with a green icon), thus breaking off pieces of the ice to use as platforms.

BOSS FIGHT: "UNKNOWN RECYCLING WEAPON"
Once you finally reach the very end of Tamsui River, you'll have to defeat the boss, "Unknown Recycling Weapon". This boss is a large sphere that levitates off the ground. It's not super difficult, but it has two phases and a few heavy-hitting moves worth mentioning.

In Phase 1, it mostly just sits in place and lets you attack it. As for its attacks, firstly, it will often open its "mouth" and shoot bits of trash at you that includes intact robot cores. Be careful around them, because if you get too close and/or hit one, they explode. The boss can also make them explode as he can hit them, too.  His other main attack is shooting a large red laser beam at you, which is quite strong and can be rather painful, so you're going to need to take care to avoid that.

In Phase 2, it keeps the same attacks as before, but adds another two. At some point, it will raise up in the air, open its mouth, and shoot massive rocks that will land all around the arena. You are meant to use these rocks as cover for when it shoots lasers or trash at you. However, after a period of time, it will open its mouth and pull all of the rocks back into it, and you alongside them. You'll have to fight the gravity pull by constantly running in the opposite direction, and/or dodging away.

Just keep melting it down until you get through its armor and can use a Break Strike on him. Once you get him into that Break State, it falls on the ground and opens its mouth, revealing its vulnerable core within. Attack that with everything you've got, perhaps a Burst if you have it, and you'll be able to destroy it.